Electron Focusing Lens

For a Modulated X-ray Source

Documentation and Downloads

  • All Daily Presentations (.zipx)(.zip)
  • Project Assignment (.pptx)
  • Midsummer Lunch Presentation
  • PERT Chart
  • WBS (.docx)(.pdf)
  • Final Poster (.pdf)
  • Final Report (.pdf)
  • Prototype 1 Simulation Files(.zip)
  • Prototype 2 Simulation Files (.zip)
  • Java Interpreter Files (.zip)
  • Daily Updates

    August 4

    Very quick update - You can find our simulation files above or right here for the first and second prototypes that we actually machined. Included in each zip file is the .GEM, .fly2, and .rec files for SIMION that we used to simulate the various lens configurations. We've also posted our Java interpreter, written by our own Kevin McClure, to help make sense of the data. Have fun simulating!

    Prototype 1
    Prototype 2
    Java Interpreter

    August 1

    We got results from the testing of our final prototype last week, but realized belatedly that the dimensions of the powered electrode were not quite what we had expected. Specifically, the inner diameter of the powered electrode was 0.14" where it should have been 0.3", which explains why we got some very strange results, as can be seen in the following graph:

    ...look at the final report?

    Regardless, it would seem that for a certain range of voltages, our experimental results are better than what our simulations predict. Nevertheless, it's unfortunate that we don't have the time to fix these dimensions and get better results.

    In other news, we're done with the project! Our final report can be found here and our final poster can be found here.

    July 25

    We ran a final round of simulations over the weekend to follow up on the observations that Mark Somerville made at our last meeting with him. We chose to explore plate lengths ranging from 0.2-0.6" for two different inner diameters, and the results of our simulations can be seen in the following figures:

    Not hereGone!

    We can actually see from these simulations that the combination we chose for our final prototype - 0.1" first plate length, 0.4" second plate length, 0.3" inner diameter - will yield one of the smallest spots observed among these simulations, which is pretty exciting. Hopefully, Steve will be able to send us images verifying these simulation results sometime today or tomorrow.

    July 22

    We talked with Mark Somerville yesterday just to verify our experimental results from a theoretical perspective. He was able to point out to us that the lens will operate differently if the individual outer diameters of the plates are less than their length than if the two quantities are equal/greater. We may run simulations between the two different regimes over the weekend. In the meantime, we have already sent the drawings to Steve at Goddard, who has passed them on to his technicians. Hopefully, we'll be able to test the lens on Monday and get another round of results.

    We also did some more analysis on the images. We first measured the diameters of the brightest spots in each image by hand, and then wrote a MatLab program to take the maximum values of each pixel per row and column of the image. We then compared them to the average diameters predicted by our simulations, the results of which can be seen in the following graphs.

    Not hereNot here

    July 19

    We went back to do more simulations of the lens and discovered one potentially major error - whenever we changed the spacing between the plates, or the length of the plates, we didn't ensure that the distance to the target was the same in all cases, so the target's effect on the electron beam was variable instead of standardized. After a brief group huddle, we decided that it would be best to correct our error for the round of final simulations we would be running with our four chosen lens configurations instead of trying to continue with the same parameters as before. We figured that we might as well put the time into making sure that these simulations were as correct as possible.

    The four lens configurations we tested only differed in terms of their first and second plate lengths. Otherwise, they all had a 0.49" outer diameter, 0.3" inner diameter, and 0.078" spacing between the plates. We ran simulations for combinations of first plate lengths of 0.1" and 0.2" and second plate lengths of 0.4" and 0.5". The results of these simulations are below:

    It's gone missing. Check back in a bit?

    We've decided to go with the 0.1"-0.4" combination just to minimize overall length, since Steve and Keith voiced concerns about the mass of the copper. We'll be machining our final prototype today, if the machine shop is open. We might also be redoing some of our old simulations, if time allows.

    July 18

    We did some preliminary analysis of our results and discovered that at higher voltages, while the width of the spot decreases, the overall intensity of the image decreases. After consulting Keith, however, it would seem that we ought to disregard the extraneous spots around the bright core of each image, since those are due to higher-energy X-rays that pass through the pinhole. He was able to send us a report done by a graduate student in his lab last year on the pinholes used in the CCD camera and their effects on the images taken. We are now convinced that the overall width of the bright core is the component of the image on which to focus our efforts.

    Today, we went back to SIMION and ran more simulations with positive voltages ranging from 0 to 500 V, again to test the relationships between plate lengths, spacings, and diameters. We felt this was important since we were going to move forward with testing primarily positive voltages. We're also continuing to process the images and hope to be able to present data on the FWHM of the intensity profiles of each image. We are also working on a color-mapping of the greyscale images we have for the purposes of easy visualization. Finally, we are working on redesigning our lens so that we can machine our final prototype on Wednesday. So far, we have reduced the overall length from 1.05" to 0.6", and plan to change the method of powering the lens so that it doesn't interfere with the overall operation of the lens.

    We may ask Steve to run additional tests on our lens while using different pinhole sizes, just so we can verify the effects of the pinhole on our results. If time allows, we would also like to see if removing the lens from the MXS will cause the flower-like patterns to appear in our test results.

    July 15

    We have received our testing results!! Whoopee!! Since then, we have been trying to find the best way to analyze the data in order to determine what the best voltage to hold the second electrode at and if our simulation results match up with the actual results.

    We've also been working on our final report and poster. We're planning on producing another prototype of the lens on Wednesday when the Machine Shop is open, and hopefully have it tested before our project comes to a close.

    July 13

    We don't have testing results quite yet, but Steve over at GFSC was able to get the multiplier re-coated and the quartz rod on the LED repaired, so we should get some better results soon. He noticed that there was a current draw from the target at higher voltages and decided to try to take the voltage on the lens up to higher values so that there would be a constant current draw.

    In the meantime, we will continue to design our final prototype and write our final report.

    July 12, 2011

    Good news is that we've got some data! You should be able to see it in the Simulation section soon. Positive voltages on the middle plate causes the CCD camera to detect 10x more X-rays than with no voltage on the middle lens! Bad news is that the negative voltages didn't behave the way we expected. We actually got a smaller X-ray output than when we had 0 V on the middle plate, so our lens would be doing more harm than good at a negative voltages. So, our simulations aren't accurate for negative voltages, but after doing some rough calculations with the dimensions of the image, predicted spot size, and various parameters of the testing steup, we figured out that our predictions for the spot size under positive voltages are within a millimeter or so of the actual spot size. So, we ran more simulations with our final geometry under positive biasing conditions and asked that our lens be tested from 100 - 300 V today. So, all that we're doing for today is sitting tight and waiting for results to trickle in.


    July 11, 2011

    Good news: NASA got our lens set up! Bad news: Seems we are emitting x-rays when only the target is biased. We think the problem is that the wire feed-through is emitting electrons which are hitting the target. So Keith and Steve are cleaning the parts we shipped to them and going to realign the system to see if that helps fix the problem. Also, there was no morning meeting today.

    Update: Steve was able to do two successful tests at 0V and 80V, but when we Skyped with him the software was not cooperating. He left to trouble shoot the problems, but said he would run some tests when he gets the chance. The team is now beginning to celebrate a teensy bit because our lens would appear to be working! We have no idea how well, but we do know that we didn't make it worse! Woohoo!

    July 5-8, 2011

    What a week. This was by far the busiest we have been between the holiday, family visits, double- and triple-checking simulations, machining the lens, mailing the lens, and getting the first round of feedback from Goddard. (Not to mention we're still busy with another project each...) Even if this update is a little late, it's here nonetheless. On Tuesday (7.5.2011) we did everything we could think of to our finalized lens in SIMION, and got some spectacular failures as a result. Overall it performed remarkably well, and by the evening we had to force our perfectionist sides to give up on making it better and accept that it was only a first prototype. We submitted part sheets to Dave in the machine shop Wednesday morning (7.6.2011) and he had our lens machined inside of a few hours. (Thanks Dave!) After experimentally determining (and some slight panic) that it was a few tenths of a millimeter too big on one end, we used a file and sandpaper to put the finishing touches on the lens: a tapered end and some channels for the wires to run through. Thursday (7.7.2011) was spent assembling and disassembling the lens while checking the electrical connections within to make sure everything was in working order. That afternoon we packaged and mailed the MXS back to Goddard via overnight UPS and one wary UPS Store employee, ("You guys aren't mailing rocket fuel.. right?") and they recieved it the next morning. Friday (7.8.2011) was spent decompressing and waiting as Keith, Steve, and their intern set up the source and a CCD to capture an image of the X-rays produced. All in all it was an exciting, if not stressful, week. I could make some claim as to when the other parts of the website will be updated, but that'll probably end up being an empty promise again. We're pushing out little updates as we can; the fact of the matter is things are changing so quickly it's hard to keep everything up-to-date. Our goal is to have simulation results, details of our first prototype, and preliminary results from the field testing of the prototype up soon. Your patience is welcome and greatly appreciated.

    There were fewer daily meetings this week as well, and as such we only have two daily updates for you:



    July 1, 2011

    And it's the weekend! Today we simulated different inner and outer diameter dimensions for the three-lens version of our design. We're also re-writing our interpreter program to find the middle of the spot on the target, then tell us the average distance from that center that each electron hit. That way each ion contributes to our metric for judging a lens rather than the two that are the most spread apart in the y and z planes. We feel like this won't change the results too greatly, but it will ensure that there aren't any irregularities hiding within the spot on the target. We'll be back after the holiday weekend, happy 4th of July everyone!

    Morning Presentation

    June 30, 2011

    Today we had a lunchtime presentation to inform the other students and faculty staying at Olin over the summer about the Olin/NASA internship and about our project specifically. (Presentation avalible here.) There was also lots of digging through data during our morning meetings, and graphs have started to be made. There's a large quantity of data returned from our simulations so we're still working out the best ways to represent as much as we can on as few final charts as we can. We expect to run more simulations on Saturday (7.2), since 3/4 of the team is otherwise occupied tomorrow night. You can imagine our dissapointment to not be spending Friday night in the lab, but we've decided to take an evening off.

    Morning Presentation

    June 29, 2011

    The team just got back from the computer lab after an evening of running simulations. 14 computers, 5 hours, and lots of random outbursts of song to keep our sanity later and our first round of simulations are complete. It doesn't look as though we'll get to the three-lens simulations tomorrow; we have a lunchtime presentation to give and digging through the data from SIMION takes longer than expected. We'll begin to post results over the weekend as time permits around the holiday and family coming into town. The good news is that the simulations we ran tonight seemed to follow the trends we noticed in our earlier simulations and there weren't any big surprises hiding now that we've added the target and housing.

    Morning Presentation

    June 28, 2011

    Well, we did it. It's not the most elegant code I've ever written, but we made the geometry file approach work. Now we have the entire MXS system- housing and all- modeled in SIMION down to 0.010" accuracy. The best news is that we can validate what's happening currently with no lens in the MXS, and then focus to ~.1 mm when we insert a two-element lens. (That's roughly the size of a piece of paper, for those who can't estimate tenths of millimeters off the tops of their heads.) The machine shop on campus is only open on Wednesdays, and since we're not ready to cut today we now have a week to run simulations and try to break our design in every way possible. Tomorrow we'll test a set of 50 two-lens designs to find trends (and hopefully confirm the earlier ones) between different parameters and spot size on the target. After that we'll test the three-lens designs (Thursday) and then pit the champions against each other (Friday). Monday and Tuesday will be spent trying to break whatever lens is left, so by Wednesday we'll be confident in whatever design is left.

    Morning Presentation

    June 27, 2011

    I feel as though a bit of background is needed before this post, so here goes: We're running with the assumption that we're going to have one shot at building this lens. We don't have the capability to test it here, so once we build it we'll send it off to Goddard for testing. Ideally they could get back to us with results in enough time for us to diagnose and correct any problems and then build a new lens, but our team is working on a worst-case-scenario assumption. So we've got to get it right the first time. That being said, we found another problem with our simulations. The housing of the MXS is grounded, which creates changes in the electric field that aren't currently modeled. Time for more background! Designing in SIMION is a pain. There are probably great ways to do it, but the learning curve is so steep we've been limping along with what we can do so far. However what we can do is no longer adequate- our current method is to repeatedly add and cut away until the desired shape is created. It's like sculpting except anything you add or remove carries all the way through from the direction you're looking. And it won't work for the shapes we're trying to make now. New goal for the team: learn the programming language that SIMION uses to create geometry files so we can make more complex shapes.

    Morning Presentation

    June 24, 2011

    This morning we cracked the asymmetrical field problem! We flew through a couple of lens design revisions trying to steer the beam of electrons in such a way that the bending from the target's field will have less of an effect on spot size. (What we eventually determined was that we needed to deflect the beam upwards as it came out of the lens so that the target would pull it back down, greatly reducing the spread that happened when the target was the only thing causing a deflection.) There will be an update to the simulation section to reflect these findings soon. Long story short, it looks like we'll be losing the third electrode entirely and going with a modified two-electrode version of the einzel lens.

    Morning Presentation

    June 23, 2011

    Our Preliminary Design Review was today, and we received a number of useful feedback items from the attendees. Most significantly we were told that if we looked into other lens shapes we may be able to counteract the effect of the asymmetrical (relative to the lens) field from the target. Tomorrow we will be playing with various shapes for the third plate in an attempt to see if we can balance out in some way the 10kV target. In hindsight this seems like such a simple solution, and not only are we glad to have a new direction to work in but we've been alerted to the degree we were overthinking this project.

    Preliminary Design Review

    June 22, 2011

    Today we finally managed to create a SIMION file that allowed us to accurately simulate the target and the lens all in the same file- and we were right, the target causes all sorts of problems. The focus of the beam can't be placed up against the target because of the way the target bends the beam, it's always something like 2-3 millimeters in front of the target. The good news is that the spot size remains within ~.5 millimeter, so our goal would theoretically be met. However, based on what we've seen from the focusing abilities of these lenses, we believe we can compress the spot size even further. Tomorrow is our preliminary design review, so we will get input from faculty about the problems we've been having and be able to take that in to consideration in addition to the other things we have to work on.

    Morning Presentation

    June 21, 2011

    Unfortunately, we have confirmed that the high potential of the target having no effect on the flight path of the electrons is incorrect. By removing the lens entirely and inserting a triangular block held at 10kV, the beam undergoes a significant amount of deflection. As of yet, we are unable to get the lens and target working in the same simulation workspace, so tomorrow we will create a file that has both the lens and the target in it instead of trying to combine two different files into one workspace. One question that we still have is how (considering the large deflection we saw in the beam yesterday) the electrons manage to fly in a relatively unaffected path in the current setup of the MXS. It seems to us if there was in fact something with that high of a potential that the electrons would be deflecting within the MXS too, possibly missing the target. Either way, we hope to have more answers by the end of our meeting tomorrow morning.

    Morning Presentation

    June 20, 2011

    Today we experimented with inserting the target into the SIMION simulation. Our intution leads us to believe that having a non-symmetric, high voltage body like the target in the system would have a noticeable effect on the flight path of the electrons. However, all of the results we are getting from SIMION indicate otherwise; that there is no effect from the target. This is problematic for a number of reasons- first and foremost that it is contrary to our intuition, and obviously we are always right. (#sarcasmfont) The bigger problem is that changing the potential of the target- large positive values, large negative values, and everything inbetween- still has no effect on the flight path. We're fairly certain we're doing something absoluetly wrong, and hope to sort this out tomorrow by consulting one of the Physics professors who are on campus.

    Morning Presentation

    June 13-17, 2011

    Wow did this week fly by. As you may have noticed, the daily updates didn't exactly happen; the team got swamped by work. Anyway, we began the week by using the focus-finding program to analyze the effect of changing different parameters of the lens. The trends that we saw confirmed what our intuition suspected, the lens should have a large outer diameter and small inner diameter, be as long as the space will allow, and have as small of a gap between electrodes that we can manage. With those findings in mind, we began to (very roughly) look into options we had for fitting the lens into the MXS. At first glance, it seems simple enough, but as it turns out holding an electrode at 100-200 volts inside a 12mm diamter, vacuum sealed, grounded metal housing is a bit of a challenge. Both the simulation and hardware pages should go up by the end of the weekend, and more of the adventures we experienced this week will be detailed there. Here are the morning presentations for the week:

    Tuesday, Wednesday, Thursday, and Friday

    June 11-12, 2011: Bonus Weekend Edition!

    Over the weekend we did manage to write a program that finds the focal properties of the lens from the data that SIMION outputs, which we're very excited about. (Excited enough to bring you this weekend update in fact!) It's simple, hard to break, and gives much better answers than when we were eyeballing it before. Testing will resume tomorrow; as exciting as this is it isn't exciting enough for us to spend another weekend evening in the computer lab.

    June 10, 2011

    Tonight we had a simulation party in the computer lab, because you know, all of the cool people spend Friday night in the computer lab. We ran through as many variations of the lens as we could think of and marked down the focal properties- spot size and distance from the end of the lens- so that we can see what altering different dimensions of the lens does to the focus. However, this was taken down by hand, and isn't the most reliable although it does show trends in the simulations. Over the weekend we'll write a Java program that can more accurately find the focal properites from the data file that SIMION outputs. For now though, the team is going to enjoy the last few minutes of our Friday night by *not* working.

    Morning Presentation

    June 9, 2011

    Most of today was spent playing with different parameters in SIMION. The things we have found so far that cause variations in the beam behavior are: the radius of the rings, the distance between the rings, the length of the rings, and the charge on the middle electrode. So far we have definitively determined that the charge on the middle electrode effects the focal length of the lens but does not have a major effect on the size of the focal point. However, early indications are that decreasing the diameter of the lens causes a decrease in the diameter of the focal point of an order of magnitude to an extent but once the diameter of the focal point becomes approximately .002 mm decreases in the diameter stop having an effect. Today we hope to keep finding relationships between the parameters and focal properties, and will probably spend tonight and tomorrow night in the computer lab employing a brute-force 'how many computers can we run simulations on at once' type deal.

    Morning Presentation

    June 8, 2011

    Today we had a teleconference with Keith who answered some of the questions that we had regarding specifics of the project. At this point, it looks as though a three-electrode einzel lens will in fact be the electrostatic lens that we develop for the project. In our simulations so far, no other lens has had as good of results in as small of a package as the three-electrode version of the einzel lens. Speaking of simulations- we finally cracked SIMION! Rather than clicking every button and rarely producing useful results, we now know how to reliably use the software. The learning curve has been overcome, and the four of us are beyond thrilled. We hope to have enough simulations run by the end of the day tomorrow so that by the time the MXS arrives we can know exactly what we're wanting to put in it and start designing a new housing immediately.

    Morning Presentation

    June 7, 2011

    Most of the day today was spent playing with the SIMION software package, as the team has not heard back from our mentor, Keith, yet. Nothing against SIMION, but its interface isn't exactly the easiest to get used to... But we pressed on, and we think that we have a good enough understanding of SIMION to accomplish the modeling that we need to. The biggest thing that we discovered today was just how important knowing the electron beam properties are to the operation of the lens; the smallest changes in kinetic energy of the particles create significant changes in the way that the beam behaves as it passes through the lens. It will be important to know the characteristics of the electron beam leaving the multiplier so that we can design a lens that performs to the required specificataions.

    Morning Presentation

    June 6, 2011

    Today we had our first all-hands meeting and recieved our first feedback from Steve Holt. Overall he seemed pleased with where we were, suggesting minor changes to our PERT and SOW and offering comments on the scheduling of some aspects of our project. Accordingly, changes were made to the SOW, PERT chart, and WBS. Today we also had a meeting with Professor Mark Somerville to discuss different types of electrostatic lenses. (Specifically the difference between magnetic field lenses and electric field lenses.) This meeting provided us with enough information to decide that an Einzel lens is the type of lens that we want to use in the project. Concurrently, we have started learning the SIMION software package, and we expect to start in-depth simulation tomorrow. Our daily presentation will be made available with each daily update.