Difference between revisions of "Tagger microscope prototype construction"

Latest revision as of 20:52, 27 August 2011

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 E_γ range of 8.4-9 GeV (E_e 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 mm² 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.

Beam Test Plan
Delivery of the Tagger Microscope Prototype to JLab - James McIntyre
Spring 2011 Beam Test of Tagger Microscope Prototype - online logbook

References

Microscope Prototype Mechanical Design Drawings - James McIntyre

@@ Line 1: / Line 1: @@
-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>&gamma;</sub> range of 8.4-9&nbsp;GeV (E<sub>e</sub> 3-3.6&nbsp;GeV)
-== 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.
-[[Image:workstandassembled.jpg|thumb|Work Stand Apparatus]]
-* We designed our own apparatus to cut, polish, and glue the scintillators and the waveguides. For more information on how it works [[Work Stand Assembly]].
+== R&D Branches ==
-* To cut the fibers I use a standard hobby knife.
-* For cleaning and polishing acrylic fibers, the recommended tool to use is a plastic nail buff.
-* A digital scale (accurate to &plusmn;0.01 grams) used to weigh out the proper proportions of the resin and catalyst.
-* Glassware for weighing, mixing, and applying the epoxy.
-* A Laboratory Hotplate is used to heat cure the epoxy.
-* An inferred thermometer used for calibrating the hotplate.
+=== R&D into Fiber-Array Fabrication Techniques ===
+:''Main articles: [[Fiber Array Fabrication Techniques]]'' and ''[[Fiber Array Prototype and Mass Production]]''
-For more information (such as prices and product numbers) on the equipment listed above see [[Supplies]]
+[[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.]]
-== Fiber Research ==
+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&nbsp;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.
-=== Epoxies ===
+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
-The two epoxies that are being tested are:
+=== Scintillation Detection Sensors ===
-* BC-600 (Bicron) [http://www.detectors.saint-gobain.com/media/documents/S0000000000000001004/SGC%20BC600%20Data%20Sheet%200105.pdf/ BC-600 Info]
-* 20-3238 (Epoxies Etc) [http://www.epoxies.com/tech/20-3238R.pdf/ 20-3238 Info]
+[[Image:SSPM06_(2x2).jpg|thumb|113px|4.4&nbsp;mm<sup>2</sup> active area Silicon Photomultiplier]]
-=== Cleaving and Polishing Techniques ===
+:''Main article: [[Characterizing SiPMs]]''
-<u>Note:</u> This process is assuming 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.
-'''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
-** 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 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.
-** 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 border line acceptable proceed to Step 2.
-** 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.
-* Technique 2
-** 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 patients, 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 raped around the fiber.
-** Next, using your hobby knife make a shallow cut along your cutting guide.(Note: you don't have to cut all the way through the outer cladding, just most of the way.)  Try not to cut the inner fiber, to insure that you do not, it takes some practice.  Take a piece of scrap fiber and begin cutting the outer cladding.  The inner fiber feels much softer then the outer cladding, the only way to tell is it just cut through your test fiber.
-** 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. (Note: don't worry about scratching the inner fiber, it will all be polished away anyway.)
-** Finally, during polishing, make sure to shave the fiber almost all the way down to the cladding.
-'''Step 2'''
+=== Photo-Sensor Support Electronics ===
-* <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 border line unacceptable, see if the cladding is broken too far as not to be recovered by polishing.
-* <u>Waveguides:</u>  With that extra 1/2 cm you alloted yourself, it should be possible to recover, through polishing, most if not all the unacceptable fibers.
+:''Main article: [[Design and prototyping of SiPM electronics]]''
-'''Step 3: Polishing'''
+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.
-* 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).
-**<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.
-* 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  (if you consider the up and down motion as one complete cycle the speed should be around 1 revolution per second).  I know that these direction 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 why you do not want to go too fast or apply too much pressure is that it could (and most likely will) result 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. This process should take about 30 seconds depending on how much you need to shave off.
-* 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 you did with the emery boards but still some care needs to be taken. Basically follow the same process 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 or round off the ends. If the ends are rounded, the epoxy will not adhere properly to the fiber.
+=== Mechanical Design of the Tagger Microscope ===
-* Here are pictures of what the fiber should look like after each step [[Fiber Pictures]]
+:''Main article: [[Tagger Microscope Mechanical Design]]'' ([[User:Senderovich|Igor Senderovich]], [[User:mcintyre|James McIntyre]])
-=== Gluing ===
+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.
+* [http://zeus.phys.uconn.edu/~senderovich/GlueX/Tagger/Reports/MicroscopeBeamTest_plan-2-2010/MicroscopeBeamTest_plan-2-2010.pdf Beam Test Plan]
+* [[Delivery of the Tagger Microscope Prototype to JLab]] - [[User: mcintyre|James McIntyre]]
+* [https://docs.google.com/document/pub?id=1yC9U8ufcUvTR00vY2vNM_G78fwLKALBip3E1Zsic1R4&amp;embedded=true Spring 2011 Beam Test of Tagger Microscope Prototype] - online logbook
+== References ==
+* [[Microscope Prototype Mechanical Design Drawings]] - [[User: mcintyre|James McIntyre]]