Journal Entry 06-29
Monday, June 25th:
For the past two weeks, we have been on an extensive cleanup effort of Magnetometer lab building 253, our workplace for the duration of the summer.
Since magnetometer fabrication is being moved to other facilities located at JPL, Neil Murphy (our mentor) has been given the opportunity to take over a magnetometer building for his own Helio-seismology project. But before work on the on project, cleanup of building 253 is in order. In this cleanup effort, we have been greatly aided by one of the former magnetometer specialists that used to work here, a man named Richard Grumm. And so we worked on this cleanup effort until the debris had been cleared away so we can work in a comfortable environment.
Tuesday, June 26th:
Today we started the first line of experiments that our mentor had planned for us to conduct. This experiment would involve us using an optical bench; we first had to devise a plan of mounting the various optical instruments that would be used in our upcoming experiments. We concocted a plan for attaching to the optical bench a laser light source, photo detector diode, and two-calcite polarizer crystals. These components were arranged along the optical bench, so that the light from the laser source would pass through the calcite polarizers all the way to the photo detector where its intensity would be measured.
Today’s series of experiments involved us determining the behavior of two calcite polarizers, as they were rotated with respect to one another, while a laser beam was passed through optical axes. The goal of the experiment was to map the intensity curves around the point where the two polarizers were “crossed”, the point where the intensity of light, drops to an absolute minimum. The data curves generated from this arrangement would then form the baseline result which could then be compared to the data from other, different, experimental runs.
The results of this experiment proved to Neil that some redesign work to the experimental arrangement would be necessary in order to fix some unforeseen problems exhibited by the data set.
Wednesday, June 27th:
Today’s experimental run, Neil had everybody review the experiment of yesterday but with one modification: Neil had secretly reoriented the second polarizer so that it would extinguish the component of partially polarized light being emitted by the laser light source. This would eliminate the multiple extrema that was exhibited by the graphs of the extinction curves. The result of adjusting the second polarizer is exactly what Neil was looking for with the local extrema now falling on top of the absolute extrema produced when the calcite polarizers are crossed.
Thursday, June 28th:
Today we are in the process of redesigning the light source for the optical bench experiments. Neil said, “its a better idea to base the upcoming series of experiments on a new kind of light source”, that is, a halogen light source. The source of light puts out a broad range of light frequencies that would enable it to be immune to the kind of partial polarization effects exhibited by the laser light source. This halogen light source requires a complete redesign of the optical bench instruments, and the redesign of this light source that would be the focal point of our work for the week.
Journal Entry 07-06
Friday, June 29th:
We have rebuild the light source for the optical bench, we can now began a series of experiments that require us to do the first initial run of experiments that would show the behavior of the two-calcite polarizer system using the new halogen light lamp. To accomplish this goal, Neil divided us into teams. Amir Rivas and I (team 1), Nick Marino and Ebrain Mirambeua (team 2). Both teams would gather data using a different method. The idea of using two separate teams, each team using two separate methodologies to gather the data. This would ensure Neil that he would be able to determine the best techniques for acquiring the data in future experimental trials.
Monday, July 2nd:
Today’s experimental run, Neil wanted to see the effect on the data set of the presence of a mock MOF cell that doesn’t contain any gas whatsoever when placed between the calcite polarizer crystals. The result that’s determined indicates that no effect occurred as a result of the mock cell’s presence.
Tuesday, July 3rd:
The experiments for today is to investigate the effect of presence of a mock MOF cell that has been placed in-between the two calcite polarizers. However, in this experiment, the mock MOF cell was to be placed inside a magnetic block assembly. Basically, Neil wanted to see if any polarization artifacts would enter into the experiments results as a consequence of the magnetic field’s presence. The results indicated that the magnetic field had little to no impact on the performance of the calcite polarizer extinction curve.
Wednesday, July 4th:
Holiday no work.
Thursday, July 5th:
Today’s experiment focused on whether there would be any light intensity variation as the glass stem of the mock MOF cell was rotated, in its magnetic block assembly, while it was placed between the two calcite polarizers. The results seem to indicate that the calcite polarizers are immune to the orientation of the MOF glass cell when that glass cell is manipulated in this fashion.
Journal Entry 07-12
Friday, July 6th:
Today, our mentor wanted to know the results of placing a narrow bandwidth beam splitter in the optical path of two calcite polarizers (either ahead of the two polarizers or between them). He wanted to know if there would be any difference in the results of the measurements. So we conducted a line of experiments to determine that. We each made a number of graphs of the extinction curves around the points where the two polaizers were crossed. These results would give Neil some indication of the relative merits of the two potential beam splitter positions. Neil was somewhat pleased by the results, but felt that we needed to take more tests.
Monday, July 9th:
Neil needed more specific information in regard to the interaction of the crystalline beam splitter used in Fridays experiment, with the two polarizer system. He wanted to know the outcome to the extinction minimum, of the two crossed polarizers, which resulted from the rotation of the crystalline beam splitter that was to be placed between them. We where seeing if there would be any orientation sensitivity to the beam splitter placement in the optical arrangement. The data that we obtained was highly erratic. The result troubled Neil, and wanted to have some time to think it over. Apparently, the next experimental test that Neil had planned for us to perform was not necessary.
Tuesday, July 10th:
Today, we had to redo yesterday’s experiment, but this time Neil wanted us to use a 25/75 beam splitter. This is a beam splitter that transmits 75% of the energy that strikes it, while reflecting the remaining 25%. It has somewhat different optical properties to the crystalline, cube shaped, beam splitter that we had been using previously, and Neil hoped that this would produce more consistent looking data when placed between the two crossed polarizers. So we re-performed Monday’s experiment with this new beam splitter, which was now taking the old beam splitter’s place in the apparatus. Neil’s hunch was right, and the data produced with this new beam splitter exhibited the kind of consistency that he was seeking.
Wednesday, July 11th:
Neil left us instructions for the week (because he left out of town). He wanted us to perform the same experiment as yesterday, but this time he wanted us to measure the reflected light intensity instead of the intensity that was transmitted. In essence, the calcite polarizer closest to the light source was to be rotated, and the reflected portion of the beam splitters energy recorded for an entire rotation of the polarizer. Furthermore, the reflected beam’s energy was to be directed at a right angle to the incident beam’s direction. This data was then to be recorded on graph paper for further study.
Neil then wanted the reflected energy of a 50/50 polarizer plotted and compared with that of the previous 25/75 polarizer. Neil also wanted to see if this beam splitter exhibited any orientation sensitivity as well, and instructed us to re-perform Tuesday’s experiment using this 50/50 splitter.
Thursday, July 12th:
Today’s experimental is to see what the effect would be on the energy of the reflected beam if the beam formed an angle other than a right angle with the incident beam. Apperentally, the instrument was set up to produce a reflected beam that made an angle of around 60 degrees with respect to the incident beam, back towards the light source. This arrangement was to be used to record the reflected light energy data for both the 50/50 beam splitter as well as the 25/75 beam splitter condition. Like in Wednesday’s experimental run, the calcite polarizer was to be rotated in a circle, in two degree increments, until an entire 360 degree increment is completed.
Neil’s second task for the team was to devise a method for supporting the solar telescope tracking mechanism so that it will be positioned, on the optical bench, at right angles to the Magneto Optical Filter ( or MOF, for short ) when the telescope is finally up and running.
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Journal Entry 07-20
Friday, July 13th:
Today the participants of the CURE project met in building 183 for a meeting. Then we took a tour of some of the facilities at JPL.
Monday, July 16th:
Neil had to leave for a trip to Boulder, Colorado for an important meeting, so he had left instructions for us to follow for the upcoming few days. He had requested that we write up a full report on all the experiments that we had completed. We started work on the report the today. We had to rethink everything we had done so far, and we had the opportunity to clarify many of the experimental observations that we had performed.
Another assignment that Neil assigned us to work on was to find a way of mounting the Heliostat (a device used to accurately track the path of the sun as it moves across the sky throughout the day) to the optical bench that was located just beneath the periscope like tube of the solar telescope. Essentially, we had to develop a method for mounting this device so that a more permanent fixture could be fabricated, from this prototype, at a machine shop somewhere on the JPL site.
Tuesday, July 17th:
On Tuesday, Neil came by at 12:00 noon, to leave us with final instructions for the work that he wanted to see done for the rest of the week. Basically, Neil wanted us to review the same experiments that we had been doing for the last couple of weeks, except that he wanted us to use a sodium filter in place of the potassium filter that we had been using. For the rest of the day, we worked on the written reports of the past experiments that Neil had assigned for us to do earlier on.
Wednesday, July 18th:
As Neil was out of town today, we mostly worked on the reports that he requested that we write, describing exactly what it was we had done in the previously performed experiments
Thursday, July 19th:
Today was a day that we, for the most part, worked on various reports that needed to be generated. Anyway, with whatever time we had left, we used it to start the next series of experimental runs, the runs using the narrow-band sodium filter, which were requested by Neil.
Journal Entry 07-27
For this first experiment, we had to determine the behavior of two calcite polarizers, as their planes of polarization were rotated with respect to one another, while a beam of laser light passed through their coincident optical axes. The basic goal of the experiment was to map the intensity curves of light around the point where the two polarizers were “crossed”; that is, the point where the intensity of light, through the two polarizer system, drops to an absolute minimum. The data curves generated from this arrangement would then form the baseline result which could then be compared to the data from other, different, experimental runs.
Commensurate with this goal, the above experiment was arranged, on an optical bench, in the following manner:
1.) First, the laser light source (a pen style laser pointer) was secured in a rectangular metal block that was then fastened to the optical bench via a treaded screw.
2.) Then the two calcite polarizers were set on the optical bench in such a manner so that the light from the laser source would pass through their coincident axes.
3.) A detector, which was read by a volt-meter to the nearest tenth of a millivolt, was then placed behind the last polarizer so as to measure the intensity of the light that passed through the two-polarizer system.
4.) Finally, graphs were generated from the acquired data.
The results of this experiment were somewhat unexpected; the generated data curves exhibited, in addition to the expected absolute minima occurring at the point of extinction, local extrema occurring as a result of the fact that a portion of the laser light was partially polarized. Neil then developed a clever work around solution for this problem by aligning the plane of polarization of the second polarizer such that it was parallel with the component of partially polarized light from the laser source. This solution caused the local extrema (the extrema that were being produced by the extinction of the partially polarized component of light from the laser source) to coincide with the absolute extrema that occurred when the two polarizers were crossed. This redesigned experiment, with the re-oriented second polarizer, became the foundation for the second experiment.
As indicated above, Experiment 1 was essentially repeated with the second polarizer reoriented so as to allow the local extrema, the extrema that are caused by the extintion of the partially polarized component of light in the laser source, to fall on top of the absolute extrema that are produced when the two polarizers are crossed.
This second experiment was performed in exactly the same manner as the first, with the results being recorded on graph paper.
With the reorientation of the second polarizer, the generated data curves now exhibited the expected extinction minima; that is, the absolute minima that occur when the calcite polarizers are crossed.
The critical results are as follows:
Absolute Minima: ~4.0 mV @ ~120 degrees & ~12.0 mV @ ~300 degrees
Dark Current: ~0.3 mV
(For a more detailed representation of this data, see the attached graph section.)
June 29, 2001: The Setup and Design of the Halogen Light Source for Future Experimental Runs:
In experimenting with the laser light source used in the past two experiments, Neil concluded that the laser would not be a suitable source of light for the upcoming experimental runs. Specifically, the problem was that the laser light source operates at a wavelength that would not interact well with the cube shaped beam splitter that Neil wanted to insert into the optical path of the apparatus. Thus, a more suitable light source needed to be found, and the light source selected was a halogen lamp; a light source that is normally used as a microscope illuminator.
Since the halogen lamp produced a large number of non-parallel rays of light, a method by which these non-parallel components could be focus, and concentrated, needed to be found. Thus, the remainder of the day was occupied with an effort to build the necessary tubing and lenses that would be used to conduct the halogen light, through the arrangement of polarizers and beam splitters, to the photo detector at the other end of the optical bench. The assortment of equipment needed to perform this task, working from the light source end of the optical bench to the detector end, is as follows:
A.) First, the halogen light source is mounted on a lab jack and placed on the optical bench.
B.) A support post (the one with the treaded fixture so as to allow tubing to be attached) was then fastened to the bench next to the light source.
C.) On the light source side of the post there is treaded a 1 1/2-inch and a 1/4-inch (in that order) section of tubing (all empty; i.e., containing no lenses).
D.) On the side of the support post, facing away from the light source, is treaded a 1 1/2-inch piece of tubing (empty).
E.) Next, a piece of 6-inch tubing, the one containing the light baffle, is connected to the tubing already pieced together. (Note: The light baffle is positioned in the far end of the tube; that is, the end of the tube that is farthest from the light source.)
F.) Continuing in a like manner, a 1 1/2-inch piece, a single 1-inch piece, two 2-inch pieces, and a small 1/4-inch piece of tubing are attached, in that order, to the tubing already put together. (Note: All of the above tubing is empty. Moreover, a support post—an open ring style type—is secured to the optical bench and applies support to the piece of tubing that is 1 1/2-inches long.)
G.) At this point, an iris diaphragm is to be connected to the whole ensemble and then stopped down to an experimentally determined working diameter.
H.) Now a 1/4-inch piece of tubing is to be attached that also contains a ~200 millimeter focal length lens—the only lens used in the entire setup.
I.) Finally, a 1/2-inch piece of empty tubing is attached, along with a second iris diaphragm, immediately behind the other fully assembled optical conduit.
As for the optical tubing associated with the photo detector, the following listed arrangement applies:
a.) The photo detector is mounted on the optical bench vial a post with a threaded fixture.
b.) To the front side of this post—the side facing the light source—there is fitted a 2-inch piece of tubing that contains a ~50 millimeter focal length lens. This lens is placed about 3/4 of an inch into the light source facing side of the 2-inch piece of tubing.
c.) Just behind the above arrangement of tubing is placed 1/2-inch piece of tubing containing the chosen narrow band filter.
d.) This whole assemblage is then screwed into the light source facing side of the post.
e.) Behind the post is treaded a 2-inch piece of tubing that holds the photo detector in place immediately to its rear.
Experimental runs, using the above arrangement of optical tubing, were then conducted with the halogen light source set to a level of 3 on its light intensity dial. The experimental runs consisted of measurements that were made by rotating the front polarizer (the polarizer that is closest to the light source) in two, five, and ten degree increments. The duty of performing these measurements was divided among two teams, and the results of each team’s effort were then plotted separately.
June 29, 2001: Experiment 3: Determination of the Baseline Behavior of the Two Calcite Polarizer System Using the Halogen Light Source:
With the halogen light source put together on the optical bench as described above, a series of experiments, designed to characterize the behavior pattern of the calcite polarizers, was initiated. This experiment was conducted by two teams: one team would do the experiment in five or six degree increments, while the other team would do the same experiment in either one or two degree increments.
The goal of the experiment was to map the response curve of the two-calcite polarizer system. This was done by rotating the first of the two polarizers, in increments of either five or two degrees, until a full 360-degree rotation had been completed. The baseline response curve, of the two-calcite polarizers system, was then generated from the acquired data.
Results:
This experiment produced minimum detector voltage values, at around the extinction points, of about 0.8 mV for the minimum occurring at ~120 degrees, and 0.6 mV for the minimum occurring at ~300 degrees.
July 2, 2001: Experiment 4: The Determination of the Effects, on the Data Set, of the Presence of a Mock MOF Glass Cell When Placed Between the Calcite Polarizers:
This experiment required that we place a mock MOF glass cell (unfilled with any gas) between the two-calcite polarizers to see if any polarization effects would be introduced into the acquired data stream. For this experiment, the interest was focused on the intensity of light that “leaked through” the crossed polarizers at the extinction points. Consequently, the data was gathered at plus and minus ten degrees, in one-degree increments, above and below the 120 and 300-degree minima.
Results:
As for this experiment, the acquired data demonstrated that little to no effect occurred as a result of the mock cell’s presence:
Without Mock Cell With Mock Cell
~120 Degree Extinction | 0.8 mV / 1.1 mV
~300 Degree Extinction | 0.6 mV / 0.6 mV
Dark Current: 0.3 mV
This was an unexpected result as it was thought that the presence of the mock MOF cell, between the calcite polarizers, would impact the values of the extinction minima more severely than it actually did. However, the graph section of this experiment indicates that the extinction curve generated by the presence of the mock MOF glass cell was slightly offset relative to the baseline extinction curve generated when the glass cell is absent.
(Note: An extinction curve is defined as a graphical mapping of the transmitted light intensity near the point where the two-calcite polarizers are crossed. This mapping will entail a graph of the intensity of light versus the angle of orientation of one of the two calcite polarizers.)
July 3, 2001: Experiment 5: The Determination of the Effects of the Presence of a Mock MOF Glass Cell, Imbedded in a Magnetic Block Assembly, that is Placed Between the Calcite Polarizers:
In this experiment, the mock MOF glass cell, the one that was used in the previous experiment, is placed within the confines of a magnetic block assembly. This entire assembly is then supported by an optical bench jack and positioned between the calcite polarizers. The glass stem of the mock MOF cell was then positioned in one of two possible orientations, which were, arbitrarily, labeled left (L) and right (R). In addition, the entire magnetic block assembly had two possible orientations with respect to the light source—these orientations were labeled Red and Green. Finally, it was decided that both the handedness and color orientations of the mock MOF block assembly were to be referenced as facing the light source so as to provide a standard frame of reference for each experimental run.
Since the experiment was to again focus on the behavior of the transmitted light intensity near the extinction points of the crossed polarizers, data was gathered at plus and minus ten degrees, in one-degree increments, above and below the 120 and 300-degree minima.
Results:
The gathered data was presented as a sequence of plotted curves, which overlaid one another, on the same sheet of graph paper. It was again noted that the values of the extinction points were little affected by the presence of the mock MOF cell.
For example, the gathered data produced the following results:
Angle of Minimum: Orientation of MOF Cell: Voltage Reading at Minimum:
120 degrees Green, Right (R) 1.0 mV
Green, Left (L) 1.0 mV
Red, Right (R) 1.1 mV
Red, Left (L) 0.8 mV
300 degrees Green, Right (R) 0.6 mV
Green, Left (L) 0.6 mV
Red, Right (R) 0.6 mV
Red, Left (L) 0.7 mV
To get a sense of how little this variation is, compare these results with the baseline values:
Angle of Minimum: Orientation of MOF Cell: Voltage Reading at Minimum:
120 degrees No Cell Present 0.7 mV
300 degrees NO Cell Present 0.5 mV
Dark Current: 0.3 mV
However, as also witnessed in the preceding experiment, the extinction curves generated by the presence of the mock MOF cell exhibited a slight offset with respect to the baseline curve. (See the attached graph section.)
July 5, 2001: Variation of the Transmitted Light Intensity Through the Mock MOF Cell, as the Glass Stem of the MOF Cell is Rotated from Left to Right:
In this experiment, the investigation centered on whether or not there would be any light intensity variation as the glass stem of the MOF cell was rotated from left to right (through roughly a 60 degree angle) at angular points near where the two polarizer were crossed. More specifically, the calcite polarizers were oriented, in one-degree increments, above and below the point where extinction occurs. At each of these angles, the glass stem of the MOF cell was rotated from left to right. This experiment was repeated for all of the angles that laid within plus or minus five-degrees of the extinction points (eleven angles in all).
The following is a sample of the manner in which the data was acquired:
120 Degree Minimum, Green Side of MOF Block Assembly Facing Light Source:
Angle of Polarizer Intensity Range Intensity Variation:
(degrees): as Cell is Rotated:
115 29.4 mV to 29.8 mV 0.4 mV
116 18.4 mV to 18.5 mV 0.1 mV
117 11.9 mV to 11.9 mV 0.0 mV
118 6.2 mV to 6.2 mV 0.0 mV
119 1.8 mV to 1.8 mV 0.0 mV
120 0.7 mV to 0.7 mV 0.0 mV
121 1.0 mV to 1.1 mV 0.1 mV
122 3.6 mV to 3.7 mV 0.1 mV
123 8.0 mV to 8.2 mV 0.2 mV
124 14.1 mV to 14.3 mV 0.2 mV
125 20.6 mV to 20.9 mV 0.3 mV
Dark Current: 0.3 mV
Results:
All of the combined data indicates that there is very little intensity variation, near the extinction points of the calcite polarizer system, as the glass stem of the MOF cell is rotated. The only intensity variation seen was probably signal strength dependent. Consequently, as the signal strength is very weak when the calcite polarizers are crossed, the signal variation caused by the rotation of the MOF cell, at this point, is too low to be detected. Thus, the MOF cell is pretty immune to the exact orientation of the glass cell that is placed between the magnetic blocks.
July 6, 2001: Determination of the Best Point to Place a Cube Shaped Beam Splitter:
This experiment tries to establish the best place to position a “cube shaped” beam splitter; that is, it tries to determine whether it would be better to place the beam splitter between the two polarizers or to one side of them. Thus, both possibilities needed to be explored, and separate experiments were designed for each case. Furthermore, a potassium narrow band filter was positioned inside the photo detector in manner described in the June 29th entry. This filter will remain as part of the detector until noted otherwise.
Case 1: The cube shaped beam splitter was placed on the light source side of the calcite polarizer ensemble. Since it was only the behavior of light near the extinction points that was of interest, we only needed to generate curves for the angular range that was plus or minus 5-degrees on either side of each extinction point.
Case 2: The cube shaped beam splitter was now placed between the calcite polarizers. Since, as before, only the behavior of light near the extinction points was of interest, we only generated intensity curves for an angular range of plus and minus 5-degrees around each extinction point.
Results:
The following table lists the pertinent results:
Beam Splitter to One Side of Polarizers: Beam Splitter Between Polarizers:
Minimum: Voltage: Minimum: Voltage:
120 degree 0.7 mV 120 degree 0.9 mV
300 degree 0.5 mV 300 degree 0.8 mV
Dark Current: 0.3 mV
It should also be noted that, as in previous experiments, the generated data curves were offset relative to one another. (See graph section.)
July 9, 2001: Determination of the Sensitivity of the Cube Shaped Beam Splitter to Orientation:
For this experiment, we needed to determine the effect on the extinction minima that occurred as a consequence of the beam splitter, which was placed between the two polarizers, being rotated through a full revolution in 45-degree increments. Since rotation of the beam splitter would be rather difficult, it was decided to rotate the second polarizer, the one farthest from the light source, through the 45-degree increments instead.
Results:
The results that were produced were somewhat disappointing, as the data did not exhibit the kind of consistency that was thought to be possible with this kind of beam splitter. The table presented below will give an indication of the kind of problems presented in the data set:
Angle of Second Polarizer: Angle of First Polarizer: Extinction Minimimum:
O degrees 131 degrees 5.3 mV
303 degrees 10.7 mV
45 degrees 77 degrees 122.4 mV
157 degrees 116.0 mV
90 degrees 33 degrees 10.5 mV
212 degrees 9.5 mV
135 degrees 168 degrees 24.4 mV
248 degrees 24.0 mV
180 degrees 125 degrees 1.5 mV
335 degrees 1.5 mV
225 degrees 79 degrees 31.6 mV
259 degrees 29.0 mV
270 degrees 34 degrees 2.8 mV
212 degrees 2.2 mV
315 degrees 165 degrees 28.8 mV
346 degrees 28.4 mV
Dark Current: 0.3 mV
Clearly, another method of light beam splitting would need to be found in order to produce more consistent results. Neil thought that the use of a “plane style” beam splitter might yield more consistent data, and so this suggestion became the foundation of the next series of experiments.
July 10, 2001: Preliminary Determination of the Suitability of the Use of a “Plane Style” Beam Splitter (75/25):
As the use of the cube style beam splitter was proving to be somewhat problematic, a different type of beam splitter was elected for use. This beam splitter was of the planer type, and it had a transmittance to reflectance ratio of 75% to 25%--the so-called (75/25) beam splitter.
The main purpose of this first experiment was to test this new beam splitter’s suitability relative to the cube shaped beam splitter that was used in the previous experimental trial. Thus, this (75/25) beam splitter was positioned between the two calcite polarizers in a manner similar to the one used in the previous experiment, and its beam of reflected light energy directed at right angles to its beam of incident light energy. The experiment was conducted by rotating the second polarizer through a full revolution, in 45-degree increments, until the location of all the extinction minima was recorded.
Results:
The tabulated results are follows:
Angle of Second Polarizer: Angle of First Polarizer: Extinction Minimimum:
O degrees 125 degrees 1.6 mV
305 degrees 1.8 mV
45 degrees 85 degrees 52.0 mV
265 degrees 50.1 mV
90 degrees 37 degrees 1.6 mV
216 degrees 1.4 mV
135 degrees 171 degrees 46.0 mV
351 degrees 46.1 mV
180 degrees 128 degrees 1.9 mV
308 degrees 2.1 mV
225 degrees 84 degrees 53.9 mV
264 degrees 52.1 mV
270 degrees 33 degrees 5.2 mV
212 degrees 4.6 mV
315 degrees 165 degrees 47.5 mV
345 degrees 47.9 mV
Dark Current: 0.3 mV
Although the plotted data conveys the consistency of these results much more convincingly, it is still evident, even from this tabulated form, that the behavior of this beam splitter is vastly superior to that of the cube shaped beam splitter. Neil was so impressed with this data sets consistency that he ordered an entire new round of experiments to be performed using this “plane style” beam splitter exclusively.
July 11, 2001: Mapping the “Plane Style” Beam Splitter’s Interaction with the Calcite Polarizers by Observing the Transmitted Light Energy:
For this experiment, the (75/25) “plane style” beam splitter was to be positioned between the two calcite polarizers, and the transmitted light intensity recorded for a full revolution of the first polarizer while the second polarizer was to be held in a fixed position. The beam splitter was also to have its reflected energy directed at right angles to its incident energy. Furthermore, the data was to be gathered in two-degree increments and plotted on graph paper for future reference and further study.
Results:
See the attached graph section for the plotted data (the curves are most curious looking).
July 11, 2001: Mapping the “Plane Style” Beam Splitter’s Interaction with the First Calcite Polarizer by Observing the Reflected Light Energy at Right Angles:
The (75/25) beam splitter was again used as the object of study in this experiment. This beam splitter was placed between the calcite polarizers and had its reflected energy directed at right angles to its incident energy. However, for this experiment the intent was to map the intensity of the reflected light as the first polarizer was walked through a complete revolution in 2-degree increments. The intended purpose of this experiment was to reveal any polarization attributes that the beam splitter might introduce into the data stream, a quality that would be discovered as the plane of polarization of the first polarizer was rotated. The results of this experiment were then represented graphically.
Results:
See the attached graph section for the plotted data.
July 11, 2001: Mapping the “Plane Style” Beam Splitter’s Interaction with the First Calcite Polarizer by Observing the Reflected Light Energy at a 45-Degree Angle:
The (75/25) beam splitter was positioned between the calcite polarizers as before except that, instead of directing the reflected light energy at right angles to the incident energy, the energy was directed at a 45-degree angle back towards the light source. This experimental arrangement would yield information as to any sensitivity the beam splitter possessed relative to non-orthogonal incident and reflected energies.
Results:
See the attached graph section for the plotted data.
July 12, 2001: Determination of the Suitability of Using a (50/50) “Plane Style” Beam Splitter:
The following experiment is actually a series of experimental runs designed to test the feasibility of using a (50/50) “plane style” beam splitter. This experiment is essentially a repetition of the experimental sequence that started on July 10th and continued through July11th. The only difference between these two experimental sequences will be the use of a (50/50) beam splitter in place of the (75/25) beam splitter that had been used previously.
A listing of each of these four experiments will now be provided as a reference:
Experiment 1: For this experiment, we needed to determine the effect on the extinction minima that occurred as a consequence of the (50/50) beam splitter, which was placed between the two polarizers, being rotated through a full revolution in 45-degree increments. Since rotation of the beam splitter would be rather difficult, it was decided to rotate the second polarizer, the one farthest from the light source, through the 45-degree increments instead.
Experiment 2: For this experiment, the (50/50) “plane style” beam splitter was to be positioned between the two calcite polarizers, and the transmitted light intensity recorded for a full revolution of the first polarizer while the second polarizer was to be held in a fixed position. The beam splitter was also to have its reflected energy directed at right angles to its incident energy. Furthermore, the data was to be gathered in two-degree increments and plotted on graph paper for future reference and further study.
Experiment 3: The (50/50) beam splitter was again used as the object of study in this experiment. This beam splitter was placed between the calcite polarizers and had its reflected energy directed at right angles to its incident energy. However, for this experiment the intent was to map the intensity of the reflected light as the first polarizer was walked through a complete revolution in 2-degree increments. The intent of this experiment was to reveal any polarization attributes that the beam splitter might possess, a quality that would be discovered as the plane of polarization of the first polarizer was rotated. The results of this experiment were then represented graphically.
Experiment 4: The (50/50) beam splitter was positioned between the calcite polarizers as before except that instead of directing the reflected light energy at right angles to the incident energy, the energy was directed at a 45-degree angle back towards the light source. This experimental arrangement would yield information as to any sensitivity the beam splitter possessed relative to non-orthogonal incident and reflected energies.
Results:
See the attached graph section for the plotted data.
July 13-25, 2001: Repetition of the Above “Plane Style” Beam Splitter Experiments Using a Sodium Filter Instead of the Potassium Filter Inside the Photo Detector:
This series of experiments is essentially a repetition of all of the experiments that have been conducted so far with each one of the two “plane style” beam splitters. The only difference existing between these experimental runs is the use of a sodium filter in place of the potassium filter. A listing of these experimental runs will now be provided for future reference.
Experiment 1: For this experiment, we needed to determine the effect on the extinction minima that occurred as a consequence of the [(75/25) or (50/50)] beam splitter, which was placed between the two polarizers, being rotated through a full revolution in 45-degree increments. Since rotation of the beam splitter would be rather difficult, it was decided to rotate the second polarizer, the one farthest from the light source, through the 45-degree increments instead.
Experiment 2: For this experiment, the [(75/25) or (50/50)] “plane style” beam splitter was to be positioned between the two calcite polarizers, and the transmitted light intensity recorded for a full revolution of the first polarizer while the second polarizer was to be held in a fixed position. The beam splitter was also to have its reflected energy directed at right angles to its incident energy. Furthermore, the data was to be gathered in two-degree increments and plotted on graph paper for future reference and further study.
Experiment 3: The [(75/25) or (50/50)] beam splitter was again used as the object of study in this experiment. This beam splitter was placed between the calcite polarizers and had its reflected energy directed at right angles to its incident energy. However, for this experiment the intent was to map the intensity of the reflected light as the first polarizer was walked through a complete revolution in 2-degree increments. The intent of this experiment was to reveal any polarization attributes that the beam splitter might possess, a quality that would be discovered as the plane of polarization of the first polarizer was rotated. The results of this experiment were then represented graphically.
Experiment 4: The [(75/25) or (50/50)] beam splitter was positioned between the calcite polarizers as before except that instead of directing the reflected light energy at right angles to the incident energy, the energy was directed at a 45-degree angle back towards the light source. This experimental arrangement would yield information as to any sensitivity the beam splitter possessed relative to non-orthogonal incident and reflected energies.
Results:
See the attached graph section for the plotted data.
Journal Entry 08-03
Friday, July 27th:
Our day began with our weekly meeting, in building 183, to discuss both business and science related topics. On the business side of things, Rick requested that we keep up with our weekly journal reports so as not to get too far behind in their submission, and he further suggested a variety of ways in which they could be improved upon. More specifically, Rick wanted us to include, in our journal reports, the photo images that he had provided to us so as to allow these reports to have a more finished quality to them.
After the 9:30 am meeting portion of the day, we began our weekly tour of some of the facilities at the Jet Propulsion Laboratory. Our first stop was the 25-foot space environment simulator building located on the northern side of the facility. Here we were treated to a walk-in tour of a giant cylindrical room that can have its temperature varied from several hundred degrees Fahrenheit above zero all the way down to the temperature of liquid nitrogen! This room also features an array of arc lamps that can simulate virtually any level of solar light intensity desired. Moreover, this room can have its ambient air pressure lowered to 70-millitorr in approximately an hour and a half! All of this, as you might expect, was quite amazing to see.
The next stop on today’s tour found us in JPL’s robotic division. In this facility, we were presented with an assortment of robotic machinery (as you might expect) as well as a detailed explanation as to why robotic devices would enjoy an advantage over human beings when placed in a harsh, space like, environment. Additionally, we also saw a demonstration of how robotics will soon revolutionize the field of medical surgery by allowing the precise manipulation of medical instrumentation, a manipulation that will be free of a surgeon’s hand tremor.
The final stop for the day centered on a trip to the main JPL library. In this facility we were shown how the various technical reports that JPL receives are cataloged and arranged so as to make future access of these documents both fast and efficient. We were also informed on how to go about accessing this treasure trove of information by logging onto JPL’s web site.
Monday, July 30th:
Today, Neil started on the project of redesigning the heliostat tracking mechanism that will be used to guide the solar telescope for the Magneto Optical Filter work to follow later this summer. Neil and I also checked out the Santa Barbara Instruments Group (SBIG) ST-7E (Class 1) CCD camera. Apparently, there is a problem in that the camera’s shutter mechanism does not function properly. All of the team spent a good deal of time checking this problem out.
Tuesday, July 31st:
Neil, again, spent the better part of yesterday setting up the heliostat tracking mechanism for the upcoming solar telescope work. He had to completely redesign the optical path of this instrument in order to make it function well with the optical bench that had been recently installed. After Neil’s modifications, the heliostat mechanism was now ready for some trial runs in order to determine its tracking accuracy. A Nick and I were assigned to work on this project while Neil turned his attention to the malfunctioning CCD camera. Nick and I were given the task of recording the number of exposures that the camera would tolerate before failure. After this, Neil decided that the camera’s shutter was malfunctioning and in need of repair.
Wednesday, August 1st:
Today’s agenda is on the precise determination of the heliostat tracking mechanism’s ability to follow the sun without any correction being applied to its servo motors whatsoever. Basically, we waited until a representation of the image of the sun past beyond a certain prescribed point and then made note of the actual time. Then the image of the sun was re-positioned at the starting reference point and allowed to drift again. The time it took the image of the sun to do this was again noted and compared with the previously recorded time stamp. The direction in which the image of the sun needed to be moved, in order to re-center it at the reference point, was also recorded. This data was used by Neil to gain some knowledge of the heliostat’s tracking accuracy.
Thursday, August 2nd:
At the beginning of the day, Neil informed us that he had spent some time, the previous evening, working on how to get the heliostat to track without any of the “hand” correction that we had been using the over the last two days. As the redesigned tracking mechanism was lacking one of the optical beam splitters that would give it an extra degree of sensitivity and permit it to track accurately in declination, we had to settle for good tracking accuracy in right ascension alone. Neil then instructed us to again record the time it would take for the sun to drift by a certain predetermined amount, and to further take note of the direction of the correction that was needed to bring the sun back to its reference position. By the end of the day it was apparent that the heliostat was functioning as well as could be expected, and Neil expressed to us that this was a “fantastic” victory. As a consequence of this success, Neil turned his attention to fixing the malfunctioning CCD camera shutter and was able to effect repair. With the camera now fully operational, Neil’s thoughts again returned to the refinement of the design of the heliostat tracking mechanism.
Journal Entry 08-10
Friday, August 3rd:
We started the day off with our usual weekly gathering in building 183-335. Rick started the discussion with some comments on how our journal reports are to be formatted and sent to Milan Mijic. After this, Rick moved on to a discussion of the questions that he had posed to all of us last Friday.
Today’s tour involved all of us going to JPL’s Mars Yard. This is a facility that is devoted to the testing and refinement of various Mars-roving vehicles. We spent about an hour, or so, talking with the various engineers that work on the Rocky 7 and Rocky 8 explorer vehicles. During the time that we were there, one of the roving vehicles—I believe it was the Rocky 8 version—was being put through one of its automated Mars roving routines. The vehicle would move about, on the simulated Martian terrain, until it encountered an obstacle that it needed to negotiate.
Later that day, we all paid a visit to the JPL cryogenics laboratory. In this building we were treated to a demonstration of a high temperature super-conducting set of magnets that needed to be chilled to their operating temperature by a bath of liquid nitrogen. It seemed rather strange to call something a “high temperature super-conductor” when its temperature was so horribly cold in the first place. But if we compared this temperature to that of a “normal” super-conductor, which has an operating temperature that lies just a few ticks above absolute zero, then the high temperature super-conductor’s operating temperature will seem almost tropical.
While in the entryway of the cryogenics lab, we were also treated to a demonstration of the effects, on a variety of objects, of the suspension of the gravitational force. Here we were shown how the gravitational force is responsible for many of the characteristics exhibited by the everyday objects that we so frequently encounter. For example, a candle flame has the shape that it does due to the convection currents that are encouraged by gravity’s presence. Furthermore, if gravity were absent, the surface tension forces that occur between a liquid and its container become considerably more apparent. Finally, the absence of gravity allows for the demonstration of many of the concepts that are relevant to Newtonian physics such as Newton’s First Law of Motion.
As we entered into the “bowls” of the cryogenic lab, however, we were confronted with an ever-deepening array of basic science projects. Here we saw real scientists trying to answer some of the basic questions posed by their respective disciplines. This is the realm were more than just a cursory knowledge of such things as “phase transitions” and “quantum coherence” is necessary to fully appreciate the depth of the work that proceeds within these walls.
Monday, August 6th:
Today Neil wanted to establish the rate of drift in the heliostat tracking mechanism. To accomplish this goal, Neil set up the heliostat’s photo detector so that it could accurately guide the solar telescope in the right ascension axis alone. This arrangement would allow for the precise determination of the rate of drift in the declination axis that would occur as the day progressed. A time-based log of the declination axis’s behavior was then maintained so as to gain a better understanding of the overall rate of drift in that coordinate. Neil also requested that we keep track of the direction in which the sun drifted by periodically re-centering the Sun’s image along the telescope’s optical axis.
It is important to note that the telescope’s tracking mechanism had absolutely no sensitivity to drift in the declination axis. Neil simply wanted to determine if the heliostat’s photo detector was aligned precisely enough to allow accurate tracking in the right ascension axis alone. Neil also wanted to get some sort of gauge as to how well the solar telescope’s equatorial mount was polar aligned.
Tuesday, August 7th:
After yesterday’s run, Neil wanted to see if the solar telescope would track the Sun with both the right ascension and declination servos on. But, in order to allow the solar telescope to track the declination coordinate of the Sun accurately, Neil had to place a second beam splitter into the heliostat’s optical path. The second beam splitter would then allow the heliostat to become sensitive to the Sun’s drift in declination. With the heliostat now sensitive to both right ascension and declination drift, it was now possible to determine the precise orientation that the heliostat guiding mechanism’s photo detector needed to be positioned in so as to allow the solar telescope to track the Sun accurately throughout the day.
Basically, a time-based log of the heliostat’s solar tracking was produced. Neil was interested in knowing the exact time when the declination current reading was being registered on the heliostat’s power supply, shifted form a positive value to a negative one.
Wednesday, August 8th:
Today, we began the process of combining the results produced by the efforts of the prior experimental runs. The photo detector of the solar telescope’s guiding mechanism was positioned in what was believed to be an optimal orientation. However, the declination current fluctuated, from a reading of –50-microamperes to a reading of +50-microamperes. Neil noted that this fluctuation was probably the result of the photo detector being situated on the “hairy edge” of its sensitivity range. As the day’s experiment progressed, it was noted that the photo detector needed to be rotated throughout the day in order to allow the heliostat to track the Sun accurately. Although this process proved to be a rather painstaking task, we finally settled on what was hoped to be a good orientation for the heliostat’s photo detector.
Neil then reminded everyone that a “part of scientific research is precisely the kind of trial and error investigation that we had been performing all throughout the day”. Neil also emphasized that much of science is a path of creative discovery where the final outcome is not necessarily known in advance.
Thursday, August 9th:
For today’s solar tracking experiment, Neil wanted to restart the telescope with the heliostat’s photo detector aligned according to the orientation that was determined yesterday. Then at 9:30 a.m., the telescope was set tracking the Sun, and a new solar tracking log was made. The results of the Sun’s image remaining stable all the whole day. Today’s solar images were among the most stable that have been seen all week long.
Neil was very pleased with the outcome.
At end of the day, Neil came back to the lab (building 253) to make some modifications to the way in which the heliostat’s photo detector was mounted to the optical bench.
Neil installed a rotator (which was graduated in degrees) so as to allow the photo detector’s orientation to be adjusted in more precise increments. The installation of this rotator would then permit a more definitive determination of the photo detector’s angular range of sensitivity. This in turn would permit more accurate tracking of the Sun by the heliostat as the Sun changed declination throughout the year.
Neil informed everybody that he would be out of town next week until about Wednesday.
And that he would give instructions on what we work had to be done until his return.