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| − | This page contains the progress of the fabrication of the Tagger Microscope prototype. Now this is the first Wiki page that I have ever made so please excuse any errors, they will be corrected in a timely fashion. This page will be updated as the project progresses. To see what I am currently working on see [[Weekly Goals]].
| + | The '''tagger microscope''' is a movable, high-resolution [http://en.wikipedia.org/wiki/Hodoscope hodoscope] that counts post- bremsstrahlung electrons corresponding to the photon energy band of interest to the [http://www.gluex.org/ GlueX] experiment in [http://www.jlab.org/Hall-D/ Hall D] at [http://www.jlab.org Jefferson Lab]. While designed as a general-use device, it has been optimized primarily for use in the GlueX experiment, covering the E<sub>γ</sub> range of 8.4-9 GeV (E<sub>e</sub> 3-3.6 GeV) |
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| − | == Tools ==
| + | Construction of the tagger microscope prototype is now complete. Below are topics concerning the branches of the work required for its completion and testing in preparation for the construction of the fully-instrumented tagger for Hall D in Jefferson Lab. |
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| − | [[Image:workstandassembled.jpg|thumb|Work Stand Apparatus]]
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| − | * We designed our own apparatus to cut, polish, and glue the scintillators and the waveguides. For more information on how it works, see [[Work Stand Assembly]].
| + | == R&D Branches == |
| − | * To cut the fibers I use a standard hobby knife.
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| − | * For cleaning and polishing acrylic fibers, the recommended tool to use is a plastic nail buff.
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| − | * A digital scale (accurate to ±0.01 grams) is used to weigh out the proper proportions of the resin and catalyst.
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| − | * Standard laboratory glassware is used for weighing, mixing, and applying the epoxy.
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| − | * A laboratory hotplate is used to heat-cure the epoxy.
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| − | * An infrared thermometer is used for calibrating the hotplate temperature controls.
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| − | For more information (such as prices and product numbers) on the equipment listed above see [[Supplies]]
| + | === R&D into Fiber-Array Fabrication Techniques === |
| | + | :''Main articles: [[Fiber Array Fabrication Techniques]]'' and ''[[Fiber Array Prototype and Mass Production]]'' |
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| − | == Fiber Research ==
| + | [[Image:TaggerFocalPlane_ChannelPlan.png|thumb|555px|Scintillating fiber channels as seen by an on-coming electron. Since only energy tagging is required, the members of the 5-channel columns are summed to produce one signal corresponding to that energy channel. The exceptional columns are marked in red - the signals from their individual fibers will be read out to ascertain focal plane orientation and vertical spread. Note the segmentation of the 100-energy bin (column) array into 20 fiber modules. This is thought to be a more manageable design, corresponding nicely to the photo-sensor/electronics grouping.]] |
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| − | === Epoxies ===
| + | The design concept for the tagger microscope calls for a scintillating fiber detector array along the focal plane of the spectrally-analyzed beam of electrons. This is a ''two-dimensional'' array broken up into 2 mm<sup>2</sup> patches (as shown in the adjacent figure) representing the cross-sections of the square scintillating fibers. The choice cross-section of the channels is driven largely by considerations of rate. Sensitivity in the vertical direction provided by this two-dimensional array allows for a boost in tagging efficiency (matching electron angular acceptance to that of the photons they produced, which undergo collimation.) |
| | + | To avoid placing photo-sensors along the path of the electronics, the scintillation light will be delivered to separately-mounted sensors and electronics via clear fiber waveguides. |
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| − | The epoxies that are being tested are:
| + | Development of fiber cutting, polishing and gluing techniques to enable the most efficient capture and delivery of scintillation light is being conducted by Brendan Pratt and James McIntyre |
| − | * BC-600 (Bicron) [http://www.detectors.saint-gobain.com/Media/Documents/S0000000000000001004/SGC_BC600_Data_Sheet.pdf BC-600 Info]
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| − | **[http://www.detectors.saint-gobain.com/Media/Documents/S0000000000000001004/SGC_MSDS_BC600_Part_A.pdf BC-600 Part A, Material Safety Data Sheet]
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| − | **[http://www.detectors.saint-gobain.com/Media/Documents/S0000000000000001004/SGC_MSDS_BC600_Part_B.pdf BC-600 Part B, Material Safety Data Sheet]
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| − | * EJ-500 (Eljen Technology) [http://www.eljentechnology.com/datasheets/EJ500%20data%20sheet.pdf EJ-500 Info]
| + | === Scintillation Detection Sensors === |
| − | **[http://www.eljentechnology.com/msds/500AMSD.pdf EJ-500 Part A, MSDS]
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| − | **[http://www.eljentechnology.com/msds/500BMSD.pdf EJ-500 Part B, MSDS]
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| − | * 20-3238 (Epoxies Etc) [http://www.epoxies.com/tech/20-3238R.pdf/ 20-3238 Info]
| + | [[Image:SSPM06_(2x2).jpg|thumb|113px|4.4 mm<sup>2</sup> active area Silicon Photomultiplier]] |
| − | **[http://www.epoxies.com/msds/sd101_-_20-3238R_(USA).pdf 20-3238 Resin MSDS]
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| − | **[http://www.epoxies.com/msds/sd194_-_CAT_140_(USA).pdf Catalyst 140 MSDS]
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| − | === Cleaving and Polishing Techniques ===
| + | :''Main article: [[Characterizing SiPMs]]'' |
| − | <u>Note:</u> This process assumes that the uncut scintillators and waveguides are in segments or spools of more then 3 meters long. Please read each step completely before you begin this process.
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| − | '''Step 1: Cleaving'''
| + | A search for a solid state photo-sensor satisfying the tagger requirements has been conducted. The new Silicon Photomultipliers (SiPMs) are thought to fit this application better than the traditional Photo-Multiplier Tubes (PMTs) due to the nice properties of the former, including match of fiber cross section, low bias voltage and other factors. See the main page of this project for this design choice justification as well as detailed performance analysis of tested SiPMs produced by [[User:Senderovich|Igor Senderovich]] and Richard Jones. |
| − | # Technique 1
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| − | #* Place the fiber in the apparatus as shown in ''Work Stand Assembly'' under ''Cleaving''. Take the hobby knife and place it on the fiber (again look under ''Work Stand Assembly'' for the proper placement of the blade) and gently tap the butt end of the knife until the fiber is cut cleanly. Remove the fiber and inspect the freshly cleaved end. Look for any major breaks in the outer cladding (use magnifying glass if necessary). I will be posting pictures (as they become available) as to what is acceptable and unacceptable breaking in the cladding.
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| − | #* If the ends of the cleaved scintillators have major breaks in the outer cladding, then the best course of action it to toss out the unusable segment, properly polish the end attached to the spool and repeat Step 1. If the ends of the cleaved scintillators are borderline acceptable proceed to Step 2.
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| − | #* For the waveguides, it is best to give yourself an extra 1/2 cm of fiber in case the cleaved end has major breaks in the outer cladding.
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| − | # Technique 2
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| − | #* If you want to ensure that the outer cladding will not be disturbed during the polishing process you will need to remove the outer cladding for a short (about 0.5 mm) length of the fiber. This is a relatively easy process; it just takes some time, a lot of patience, and a microscope. To begin with, set up a cutting guide such that you can make a small cut perpendicular to the length of the fiber. If possible try and design your cutting guide such that it also lines up the cuts for all of the sides. I used a simple piece of paper wrapped around the fiber.
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| − | #* Using the hobby knife, make a shallow cut along your cutting guide. You do not have to cut all the way through the outer cladding, just most of the way. Try not to cut the inner fiber. To ensure that you do not, you might want to practice on some scraps of fiber. Take a piece of scrap fiber and begin cutting the outer cladding. The inner fiber feels much softer than the outer cladding. The only way to learn how to tell the difference is to slowly cut through the test fiber and feel the change in resistance. [[Image:Stripped Cladding.JPG|thumb|Fiber with Cladding Striped]]
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| − | #* Now that each side of the fiber is cut, start removing the cladding. To do this, it is easiest to use a second hobby knife. Place the second hobby knife along the cut in the fiber and place the initial hobby knife at the end of the fiber between the cladding and the fiber and use it to pry up the cladding. If you did it right the cladding should come up and break along the cut that you made. The fiber after the cladding is removed, is shown in the microscope picture to the right. (Note: don't worry about scratching the inner fiber; it will all be polished away anyway.)
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| − | #* Finally, during polishing, make sure to buff the fiber almost all the way down to where the cladding begins.
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| − | '''Step 2'''
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| − | * <u>Scintillators:</u> The segments cut using the ''Work Stand Assembly'' have an extra millimeter or so in length made by design so that by the end of the polishing process the segment will be of the proper length of 2 cm. That being said, if the fiber is borderline unacceptable, it can still be used provided that enough of the cladding is still intact to leave a sufficient length, once the defective part has been removed by polishing.
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| − | * <u>Waveguides:</u> Preparation of the ends of the clear waveguide fibers for gluing is the same as for the scintillating fibers, except that there is somewhat more freedom in the exact length of the finished fiber. If you allot 5 mm extra length when you cut the fiber from the spool then it should be possible to recover through polishing from several failed attempts to produce properly finished ends.
| + | === Photo-Sensor Support Electronics === |
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| − | '''Step 3: Polishing''' | + | :''Main article: [[Design and prototyping of SiPM electronics]]'' |
| − | * Arrange the fiber in the apparatus as shown in ''Work Stand Assembly'' under ''Polishing''. If the end to be polished is significantly longer then the desired length (i.e. 0.2 cm or more), begin with the coarse emery board . If total length is less than 0.2 cm of desired length, begin with the much less coarse nail buffs (pictures of the nail buffs will be posted).
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| − | **<u>Note:</u> It seems that the color of the nail buffs signifies how fine or coarse the buff is. So if you cannot find the exact nail buffs that I used, just try to match the color of each and you should be fine.
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| − | * Using the emery board is a bit tricky and needs special care. Gently grind down the end of the fiber with the board, do not push too hard or to soft. The strokes should be at a steady pace but not too fast or to slow. Considering one up and one down stroke as one complete cycle, the speed should be around 1 revolution per second. I know that these directions are a little obscure, so the best way to figure out just how fast and how much pressure to apply is to use a scrap fiber and practice for yourself. The reason that you do not want to go too fast or apply too much pressure is that excessive grinding speed or pressure results in stripping the outer cladding around the fiber. After the fiber is polished down with the emery board, it is best to remove it from the apparatus and inspect it for major breaks in the outer cladding. The initial grinding process should take about 30 seconds depending on how much you need to shave off.
| + | A project pertaining to design and prototyping of electronics pertaining to bias, amplification and control of the photo-sensors described above has been conducted by Brendan Krueger, [[User:Senderovich|Igor Senderovich]], and Woody Underwood. Due to the expected variability of performance of these solid-state sensors as well as variation in optical efficiency among the channels, the electronics has been designed to provide individually selectable bias voltage, controlled amplification over a wide range of light intensities, as well as feedback on "board health": state of key voltages and temperature readings at various points. Additionally, the summation of signals over scintillator channels vertical in the focal plane is incorporated. Communication with the tagger electronics for monitoring and bias control will be done of Ethernet. |
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| − | * Use the nail buffs on the fiber in the order of Black, White, Gray. I used 3 different ones because they came in a set, but if you just use the first (black) and last(gray) I think you should be fine. With these you do not have to be as cautious as with the emery boards, but still some care needs to be taken. Basically follow the same instructions as for the emery board. When you feel, through the buff, the fiber become smooth, it is time to switch to the next buff. Be sure not to over polish the fiber because it will result in rounded-off ends. If the ends are rounded, the epoxy will not adhere properly to the fiber.
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| − | * Here are pictures of what the fiber should look like after each step [[Fiber Pictures]]
| + | === Mechanical Design of the Tagger Microscope === |
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| − | === Transmission Testing ===
| + | :''Main article: [[Tagger Microscope Mechanical Design]]'' ([[User:Senderovich|Igor Senderovich]], [[User:mcintyre|James McIntyre]]) |
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| − | The main question to be answered by testing the transmission rates of the fibers is to determine how well we need to polish the fibers. This is done by cutting a 25.625” length of fiber into four segments, gluing those segments back together, testing in the dark box and comparing the results to the control fiber. The reason for the multiple cuts of the fibers is to increase the loss of photons. The increased loss of photons will make it easier to identify if the extra time taken to polish the fibers completely is necessary. The epoxy used is 20-3238. The segmented fiber will be polished three different ways; the first is using only with the emery board leaving a rough polish, the second adds the use of the three buffer boards, the third adds stripping the cladding before polishing. Being tested right now is the rough polished fiber. Testing is not yet complete but preliminary rough estimates show that there is approximately a 73% transmission through the rough fiber compared to the control. A graph and proper analysis will be posted by Wednesday afternoon.
| + | Mechanical design of the full-scale tagger microscope is well underway. The design is intended to simplify the repetitive components necessary while maximizing the flexibility of the device. In particular, the drastic dependence of the electron crossing angle with energy has been taken account: the device will have the ability for orientation of its fiber modules to match any segment in the useful energy range. |
| | + | Additionally a movable internal pulser for testing and a three-point remote-control-adjustable plane for the fiber array are under design. |
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| − | == Gluing ==
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| − | The gluing process is on-going, so there will be updates to this section.
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| − | * <u>Setup:</u>
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| − | ** There is quite a bit to set up before you begin actually applying epoxy. To start, make sure you have the following supplies:
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| − | *** Lab Gloves
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| − | *** Kim wipes
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| − | *** Digital scale
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| − | *** Acetone and isopropanol
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| − | *** A container to mix the epoxy, and a waste container
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| − | *** The resin and catalyst (or hardener) of the epoxy
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| − | *** A pipette with tip and dispensing pump
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| − | *** Tongue depressors
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| − | ** Once you have collected all the necessary equipment you can begin setting up for gluing. First and foremost, PUT ON GLOVES. Now, take out several kim wipes and place them under the digital scale, the waste container, the resin and catalyst, and on anything that could have unwanted chemicals spilled on. Set 3 or 4 tongue depressors and 3 or 4 pipettes off to the side of your workstation so that they are not in the way but easily accessible. Pour some acetone or isopropanol in your waste container for quick cleaning. Inspect all glassware to make sure that they are completely clean. If you find glassware that is not clean, clean it using acetone and then wait at least 10 minutes before using the glassware. Now that you are all set up you can begin gluing.
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| − | Here is a picture of all the new equipment that is required for the new application process.
| + | == Beam Test in Hall B at Jefferson Lab == |
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| − | [[Image:Pipette equip.JPG|thumb|center|Pipette equipment]]
| + | The ideal place to test the prototype is near another tagger magnet such as the one in Hall B. Thus the plan is to set the prototype downstream of Hall B's hodoscope. |
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| − | * <u>Epoxy 20-3238</u> | + | * [http://zeus.phys.uconn.edu/~senderovich/GlueX/Tagger/Reports/MicroscopeBeamTest_plan-2-2010/MicroscopeBeamTest_plan-2-2010.pdf Beam Test Plan] |
| − | ** Weigh out your resin and catalyst, this is a MAJOR factor in the success of the experiment so take your time in mixing and getting the exact amounts of resin and catalyst (100 parts resin to 30 parts catalyst).
| + | * [[Delivery of the Tagger Microscope Prototype to JLab]] - [[User: mcintyre|James McIntyre]] |
| − | ** Once you have the two components weighed out, mix them together. The mixture should turn mildly opaque and become viscous. When the components are mixed completely, the mixture should turn clear and the viscosity should decrease a bit, becoming more like cooking oil in viscosity.
| + | * [https://docs.google.com/document/pub?id=1yC9U8ufcUvTR00vY2vNM_G78fwLKALBip3E1Zsic1R4&embedded=true Spring 2011 Beam Test of Tagger Microscope Prototype] - online logbook |
| − | ** There will be bubbles left in the mixture. To get rid of them, just let the mixture sit for about 10 or 15 minutes and the bubbles will come to the surface. Then gently pop the bubbles with a tongue depressor. Now since the pot life of epoxy is 40 to 45 minutes, you will have plenty of time to get rid of the bubbles. [[Image:Setup Noepoxy.JPG|thumb|Fibers aligned and ready to receive epoxy]] | |
| − | ** Once you have the mixed the epoxy, lay the fibers out in the apparatus how you want them to be glued together as shown in the picture to the left. Click on the picture to get a better look at the fibers. Make sure that the ends of the fibers are clean and polished before applying the epoxy. This can and should be done while you wait for the bubbles to escape from the epoxy. | |
| − | ** Now that you have the fibers set and ready to receive the epoxy, take a clean pipette with a dispensing pump and install a tip on the end of the pipette. It is not extremely easy to tell when a tip is completely attached to the end of the pipette, so practice installing pipette tips before running through the entire procedure for the first time. [[Image:Glued Fibers.JPG|thumb|left|Fibers after epoxy has been applied]]
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| − | ** With the tip on the pipette, get a small amount of the epoxy in the pipette, and then inject it into the small gap between the two fibers. The final result should look like the picture seen to the right. Click on the photo to see a bigger image.
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| − | ** Now that the epoxy has been applied, make the final adjustments to the fibers to make sure that they are at the distance desired and that they are lined up properly. All the adjustments should be minor ones, correcting any motion that occurred during the application process. Then let the epoxy cure for 18 to 24 hours at STP, or for 1 to 2 hours at 60 Celsius.
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| − | == Protochimney ==
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| − | Note: This is not the prototype chimney to be used to couple the matrix of waveguides to the SiPMs. The "protochimney" is to be used in our dark box to couple one fiber to one SiPM. The purpose of this coupling is to test the transmission properties of cleaved fibers joined by different epoxies.
| + | == References == |
| − | | + | * [[Microscope Prototype Mechanical Design Drawings]] - [[User: mcintyre|James McIntyre]] |
| − | * Below are pictures of the completed protochimney.
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| − | {| cellpadding="3" style="text-align:center; margin: 1em auto 1em auto"
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| − | | [[Image:Protochimney submit.jpg|thumb|left|Blueprints (Produced in TurboCAD)]] || [[Image:Top.JPG|thumb]]
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| − | | [[Image:Front.JPG|thumb|left]] || [[Image:Back.JPG|thumb]]
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The tagger microscope is a movable, high-resolution hodoscope that counts post- bremsstrahlung electrons corresponding to the photon energy band of interest to the GlueX experiment in Hall D at Jefferson Lab. While designed as a general-use device, it has been optimized primarily for use in the GlueX experiment, covering the Eγ range of 8.4-9 GeV (Ee 3-3.6 GeV)
Construction of the tagger microscope prototype is now complete. Below are topics concerning the branches of the work required for its completion and testing in preparation for the construction of the fully-instrumented tagger for Hall D in Jefferson Lab.
R&D Branches
R&D into Fiber-Array Fabrication Techniques
- Main articles: Fiber Array Fabrication Techniques and Fiber Array Prototype and Mass Production
Scintillating fiber channels as seen by an on-coming electron. Since only energy tagging is required, the members of the 5-channel columns are summed to produce one signal corresponding to that energy channel. The exceptional columns are marked in red - the signals from their individual fibers will be read out to ascertain focal plane orientation and vertical spread. Note the segmentation of the 100-energy bin (column) array into 20 fiber modules. This is thought to be a more manageable design, corresponding nicely to the photo-sensor/electronics grouping.
The design concept for the tagger microscope calls for a scintillating fiber detector array along the focal plane of the spectrally-analyzed beam of electrons. This is a two-dimensional array broken up into 2 mm2 patches (as shown in the adjacent figure) representing the cross-sections of the square scintillating fibers. The choice cross-section of the channels is driven largely by considerations of rate. Sensitivity in the vertical direction provided by this two-dimensional array allows for a boost in tagging efficiency (matching electron angular acceptance to that of the photons they produced, which undergo collimation.)
To avoid placing photo-sensors along the path of the electronics, the scintillation light will be delivered to separately-mounted sensors and electronics via clear fiber waveguides.
Development of fiber cutting, polishing and gluing techniques to enable the most efficient capture and delivery of scintillation light is being conducted by Brendan Pratt and James McIntyre
Scintillation Detection Sensors
4.4 mm
2 active area Silicon Photomultiplier
- Main article: Characterizing SiPMs
A search for a solid state photo-sensor satisfying the tagger requirements has been conducted. The new Silicon Photomultipliers (SiPMs) are thought to fit this application better than the traditional Photo-Multiplier Tubes (PMTs) due to the nice properties of the former, including match of fiber cross section, low bias voltage and other factors. See the main page of this project for this design choice justification as well as detailed performance analysis of tested SiPMs produced by Igor Senderovich and Richard Jones.
Photo-Sensor Support Electronics
- Main article: Design and prototyping of SiPM electronics
A project pertaining to design and prototyping of electronics pertaining to bias, amplification and control of the photo-sensors described above has been conducted by Brendan Krueger, Igor Senderovich, and Woody Underwood. Due to the expected variability of performance of these solid-state sensors as well as variation in optical efficiency among the channels, the electronics has been designed to provide individually selectable bias voltage, controlled amplification over a wide range of light intensities, as well as feedback on "board health": state of key voltages and temperature readings at various points. Additionally, the summation of signals over scintillator channels vertical in the focal plane is incorporated. Communication with the tagger electronics for monitoring and bias control will be done of Ethernet.
Mechanical Design of the Tagger Microscope
- Main article: Tagger Microscope Mechanical Design (Igor Senderovich, James McIntyre)
Mechanical design of the full-scale tagger microscope is well underway. The design is intended to simplify the repetitive components necessary while maximizing the flexibility of the device. In particular, the drastic dependence of the electron crossing angle with energy has been taken account: the device will have the ability for orientation of its fiber modules to match any segment in the useful energy range.
Additionally a movable internal pulser for testing and a three-point remote-control-adjustable plane for the fiber array are under design.
Beam Test in Hall B at Jefferson Lab
The ideal place to test the prototype is near another tagger magnet such as the one in Hall B. Thus the plan is to set the prototype downstream of Hall B's hodoscope.
References
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