Scintillator Parts List
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Scintillation Counter Parts List
by Bob Warasila
(10/13/05)
This is our first stab at the scintillator parts list and is necessarily incomplete because of the history of the project. Presumably it will be refined with time. We’ve tried to break down the list into the principal “assemblies”: container, panel, photomultiplier tube (PMT) and electronic stuff.
CASE/Container
The case serves two purposes:
- it supports the panel and PMT assembly and
- it provides a dark environment.
After trying to design a case based on commonly available building materials we opted for a water tight gun case. These support the geometry of the counter well and since they are water tight have proven to be excellent as a light tight environment. The cheapest suitable one we have found is made by DoskoSport and is called the “Double Scoped Rifle Case” – All Weather Series W7877. Item number W7877-10819 (~$75) available from
Green Supply, Inc.
Vadalia, MO 63382
800-424-4867
http://www.GreenSupply.com
The electrical connections through the case require one (1) BNC Female to Female bulkhead style connector and one (1) 2 pin bulkhead connector for the lo-voltage DC. A gasketed connector was selected for each to maintain light tightness but that may be overkill. It doesn’t add much to the cost however. Two (2) standard male BNC connectors are required. The connector inside the case is crimped to RG174 coaxial cable. Small diameter coaxial cable is used because the wire must be fed into the cylindrical plastic case that holds the PMT. The BNC connector carries the PMT output signal for connection to the coincidence board. One (1) each of the lo-voltage connectors is required. Maintaining proper polarity on the HV supply in the PMT mount is very critical (wrong polarity cooks the supply!) so a polarized connector is important. These are the connectors we used prices range from about $2.50 to $5.00 each):
Lo-voltage bulkhead connector:
Conxall Micro-Con-X series
SC1202-ND (cable end)
SC1207-ND (panel mount or bulkhead connector)
The Micro Con is a small connector that some might find difficult to work with so here is a larger alternative also made by Conxall but called the Mini-Con-X series
SC1262-ND (cable end)
SC1273-ND (panel mount or bulkhead connector)
BNC bulkhead connector
ARFX1130-ND (Amphenol)
Although not necessary for the coincidence board if you plan to look at the signal coming out of the PMT using a digital scope you will also need these parts:
BNC Tee-Jack plug
ARFX1074-ND (Amphenol)
50 ohm BNC terminator plug
ARFX1075-ND (Amphenol)
These are all part numbers from:
Digi-Key Inc.
701 Brooks Ave. South
Thief River Falls, MN 56701
800-344-4539
http://www.digikey.com
Cushioning support materials used inside the gun case were _” floor rug padding (solid variety made of recycled materials plus foam rubber) and _” Styrofoam wall insulation. The gun cases come with urethane foam rubber inserts but we found these to be a little too thick to use more than one.
Scintillator Panel
These were supplied by Helio and are approximately 30 cm X 80 cm. The corners are cut at 45o with a 2” wide flat surface for interface with the PMT. The cut edges must be polished using the 3M polishing materials. The panel is wrapped in one layer of Tyvek but black plastic electrical tape has been also used. My best guess is that the material is the EJ-204 plastic.
Source:
Eljen Technology
P.O. Box 870
Sweetwater, TX 79556
888-800-8771
http://www.eljentechnology.com
Polishing Material:
Start with 200, 600, 1200 grit sandpaper then finish with Novus Plastic Polishes (1,2 and 3) (~$3 per 2 oz bottle) (http://www.tapplastics.com/shop/product.php?pid=113 )
Optical interface, cookie
PN EJ-560
Eljen Technology
See above
PMT Assembly
The PMT is mounted in a spring loaded set of concentric plastic cylinders. The spring guarantees good optical contact with the panel and together with the foam padding provides rigidity of the panel system. The PMTs (B51B03 by ADIT) used were a special deal arranged by Helio. They are high gain dynode style with a voltage divider base printed circuit board soldered to the pins by the manufacturer. The concentric cylinders were made at BNL out of standard plastic tube available commercially. Each tube is capped with a flat plastic end glued in place. Making these requires access to some machine tools for cutting and facing. Holes were drilled to allow passage of the lo-voltage supply to the HV module and the signal cable from the PMT.
PMT P/N: B51B03B197- including base (~$206 in quantities of 50)
ADIT
P.O. Box 870
Sweetwater, TX 79556
800-399-4557
http://www.aditpmt.com
Yes same address, same guy, different company:^)
Mu metal shields are often used on PMT to shield the electron avalanche from stray magnetic fields that may be present and degrade the gain. We’re not sure how critical this is to our application but it is standard PMT use so we included it. ADIT supplied these with the PMT tubes. Here’s another source we found on the Web:
The high voltage (HV) source is a DC to DC module that is small enough to be mounted within the concentric cylinders. We used the G20 by EMCO (~$65). We run these at 7.5 V to 8.0 V for adequate gain and stability. Polarity matters on the hook up so download the manufacturer spec sheet and be careful or you will destroy the module with reversed polarity!
EMCO High Voltage Corp.
70 Forest Products Rd.
Sutter Creek, CA 95685
800-546-3680
http://www.emcohighvoltage.com
PMT Holder hardware
Plastic materials for PMT holder (acrylic):
Hollow rods:
Cast Acrylic “Hollow Rod” 2 1/2” O.D./ 2 1/8” I.D.
PN 8486K451 (~$17/ft)
Cast Acrylic “Hollow Rod” 3” O.D./ 2 5/8” I.D.
PN 8486K461 (~$17.50/ft.)
Disc for ends:
Extruded Acrylic Disks 3” x 0.236”
PN 8581K34 (~$1.90 each)
McMaster-Carr Inc.
P.O. Box 440
New Brunswick, NJ 08903-0440
http://www.mcmaster.com
(732) 329-3200
Spring:
1 _” x 2” PN 3301 (~$3.75 each)
Century Spring Inc.
222 East 16th Street
Los Angeles, CA 90015
Toll Free: 800.237.5225
http://www.centuryspring.com
Coincidence Board
This is a custom designed board courtesy of Jeff Rothman, an engineer at the NSLS. Helio has jobbed out the circuit boards and both a parts list and an assembly manual exist on line:
Manual: Circuit Board Manual
Parts list: http://www2.sunysuffolk.edu/warasir/MARIACHI/parts.html
Circuit diagram: http://www2.sunysuffolk.edu/warasir/MARIACHI/circuitdiagram.pdf
We have had success assembling these ourselves but previous experience with soldering circuit components is obviously an important plus. Helio can supply the board but you will have to chase up the parts from the parts list on your own.
The circuit board contains a switch that allows choosing individual counters directed to the output, 2, 3 or 4-fold coincidence. Standard RG58 cable terminated with male BNC connectors can be used for the leads connecting the counters to the board. The length of the wires must be the same since we are looking for coincidences among all four counters. Our present setup places the coincidence board near the computer and brings the counter outputs to the board located there. The board requires a 5V DC (300 mA) modular plug-in regulated (5%) supply. The output of the board is a standard 10 V TTL pulse. The outputs of the counters will vary in both pulse size and rate. At 7.5 V we found the maximum pulse size to be about 400 mV and half width to be about 40 nsec. The threshold on the input can be set individually and we found ~40 mV to work on our counters, BUT check the outputs of the counters using a digital scope to get some experience with what individual counters actually put out as a pulse. The count rate of individual counters at 40 mV threshold should be hundreds of c/min and will vary between counters due to the properties of the individual PMTs. Four-fold coincidences in a room sized deployment will be an event every few minutes. Consult the manual on how to make the threshold adjustment.
Power Supply:
CUI Inc., Model No. DV-530R
Digi-Key Corp.
http://dkc3.digikey.com/PDF/T053/1560.pdf
Low Voltage DC Power Supplies
The HV supply needs to be driven by a lo-voltage power supply and so far we have chosen to use regulated power supplies. These are available in many classrooms and on E-Bay. An upper limit of 10V and 1A will be adequate to run four EMCO supplies in the PMT assemblies. A lower amperage will probably work BUT the manufacturer’s spec calls for <165 mA at minimum load so we want to be sure the lo-voltage supply isn’t being strained. In practice our setup draws ~270 mA feeding all four counters through leads ~5 m long made of copper “bell” wire.
Time Tagging
A critical element in the system is the time record that gets recorded corresponding to each event. In the interest of keeping the system simple and accurate we have so far chosen to use a high end GPS time standardization device. This is a “black box” approach that comes at a high price in $. We are using the Spectrum Instruments TM-4 Intelligent Reference (~$1400). This device comes with accessoriesincluding antenna, mounting base plate, 50’ cable, control/data cable and AC adaptor. The output of the coincidence board goes into the Reference and any events are recorded in a TXT file in the host computer. The Reference is capable of providing time and frequencies bench marks for other purposes.
Spectrum Instruments Inc.
570 E. Arrow Hghwy
Suite D
San Dimas, CA 91773
909-971-9710
http://www.spectruminstruments.com
This is an expensive solution to the time tagging problem, BUT it is a turn key solution. We have found the TM4 extremely easy to setup and reliable. We have also used a cheaper GPS device, Deluo GPS Lite ($65), but these only provide a raw signal which must be decoded and programmed into an event recording software package for the time tagging application. However if you are skilled at software development this is a cheap solution. It is definitely NOT turnkey and presented some reliability problems in our early testing.
Deluo LLC
80084 NW 53rd St.
Sunrise, FL 33351
800-693-3586
http://www.deluo.com
