Twiki for Cosmic Ray testing of SiPM-on-Tiles for CMS's HGCAL

Equipment List

Not on the Hyperdrive Rack

  • PMT x2 (with small scintillation crystals)
  • SiPM
  • Scintillator Test Tile
  • Power supplies for SiPM
  • Pulse Generator
  • LED bulb
  • DSR4
  • Computer with proper software

On the Hyperdrive Rack

  • High Voltage (HV) Supply for PMTs
  • HV Divider
  • 4 Fold Logic Unit
  • Quad Discriminators (QD)
  • LvL Adapter
  • Counter

Specifications of Equipment

  • SiPM: Hamamatsu MPPC (multi pixel photon counter), type no.: S13360-1350 PE, serial no: 30115; Dark Current (μA) 0.035, Vbr(V) 51.60, Vop(V) 54.60, Vmax(V) 56.60 (at 25 oC)
  • SiPM board: CIREXX 3517, by S. Los, Fermilab.
  • Power supply for Vbias: KEITHLEY 2410 1100V SourceMeter
  • Power supply for 6V: Tektronix PS2521G
  • Pulse Generator: Hewlett-Packard 8013B
  • HV Supply: Power Designs Pacific Inc. Model HV-1547, 1-3000V 40MA
  • HV Divider: Phototube HV Zener Divider IIX 2562-SIC
  • 4 Fold Logic Unit: LeCroy Model 365AL
  • QDs: LeCroy Model 821 (QD1) and LRS Model 621BL (QD2)
  • LvL Adapter: LRS Model 688AL
  • Counter: Jorway Dual Channel BCD Scaler Model 1880B


Follow the steps below to set up the test. Make sure all the power supplies are turned off during the setup.

Cable Connections

Instructions for how to connect all the cables between the various electronics from scratch. Usually the cables have already been connected, so you may skip these instructions. But in case of troubleshooting or setting things up from scratch, it will be helpful to read these.

When reading the instructions, you should use the pictures immediately below each set of instructions as guides. I will use "(left)", "(center)", and "(right)" in the instructions to indicate which picture to look at for a specific line of instruction. I will also use colored circles to highlight important parts in the pictures.

Tip, idea Click the images below to see them in a bigger scale and higher resolution.

LED→Pulse Generator→QD2→4-Fold Logic Unit
Inside the dark box, the LED should be connected as shown below (left), highlighted by an orange circle. Outside the dark box, make sure the top left connector, which is connected to the LED, is connected with a long cable (center). The other end of this cable should be connected to the OUTPUT(+) of the pulse generator (right). Notice from the right picture that a 2.5DB attenuator is connected to the OUTPUT(+) of the pulse generator to produce more gradual changes in the OUTPUT voltage when turning the vernier.

LED connection inside the dark box.
LED connection outside the dark box.
LED connection from the dark box to the pulse generator

From the TRIGGER OUTPUT (+), highlighted in the orange circle, of the pulse generator (left), connect a cable to one of the inputs of QD2 (center). From the output of QD2 (center), highlighted in the magenta circle, connect a cable to the INPUT C of the 4-fold logic unit (right).

A connection from the TRIGGER OUTPUT of the pulse generator
A connection from the TRIGGER OUTPUT of the pulse generator to the input of QD2, and a connection from the output of QD2.
A connection from QD2 to the 4-fold logic unit

Note that before connecting a cable to the TRIGGER OUTPUT of the pulse generator, the TRIGGER OUTPUT is first connected with an attenuator (Texscan FP-50) and an inverting transformer (EG&G Inc. IT100) (see below). The inverting transformer is there to invert the pulse to a negative pulse, and the attenuator is to make sure the vernier changes more gradually.

An attenuator connected to an inverting transformer. The combination is then connected to the TRIGGER OUTPUT of the pulse generator.

Power Supplies→SiPM and Board→DRS4→Computer
Despite the logical order implied by the title, it is easier to connect everything starting from the inside of the dark box in the order shown below.

Before following the steps below, you may want to first set up the SiPM apparatus.

Inside the dark box, make sure the SiPM board are connected correctly (left). The black cable, which is the SiPM output, is connected as shown by the green circle; the white cable which splits into 3 separate cables labeled as RTD (cyan circle), BV (magenta circle), and +6 (orange circle) should be connected as shown (center). Outside the dark box, make sure three cables are connected to the spots corresponding to RTD (cyan), BV (magenta), and +6 (orange) (right).

Connections to the SiPM board
Connections from the SiPM board inside the dark box.
Connections from the SiPM board outside the dark box

+6 (orange) goes to the Tektronix power supply (left). BV (magenta) goes to the KEITHLEY power supply (center). RTD (cyan) usually just a loose connection (right), which can be connected to a digital multimeter for temperature measurement in Ohm. For our test, we did not measure the temperature.

Connections to the SiPM board
Connections from the SiPM board inside the dark box.
Connections from the SiPM board outside the dark box

Outside the dark box, counting from the top left, the third connector is the SiPM output (green) (left). Connect it to Channel 1 of DRS4 (right). The USB connector of the DRS4 should be connected to the computer that has the DRS4 software.

SiPM output outside the dark box.
SiPM output connected to DRS4 channel 1.

HV→HV Zener Divider→PMTs→QD1→Counter and 4-Fold Logic Unit→Counter and LvL Adapter→DRS4
Like in the previous section, we will start from the inside of the dark box and work our way out.

Inside the dark box, place two PMTs in the pink foam structure (left), making sure that the sensitive part of one PMT is parallel to that of the other PMT (center), so that only a muon, which moves downward vertically and strikes both PMTs, causes a "coincidence" and triggers the DRS4. The top PMT (orange) and the bottom PMT (magenta) should be connected as shown (right). The red cables connect to the HV to power the PMTs, while the green cables are the outputs from the PMTs.

PMTs on pink foam structure.
PMTs' sensitive regions are parallel to each other.
Connections from the PMTs inside the dark box.

Outside the dark box, the connections from the top PMT (orange) and bottom PMT (magenta) are as shown (left). The red cables should be connected to the back of the HV Zener divider (center). The front of the HV Zener divider looks as shown (right). Notice the orange and magenta circles that indicate where the pins for the top and bottom PMT are in the divider. The pins are in different locations, because the two PMTs are not identical, but we still want to have similar hit rates from the PMTs.

Connections from the PMTs outside the dark box.
Connects from the PMTs to the HV divider.
Front of the HV Zener divider.

The outputs from the PMTs, top (orange) and bottom (magenta), which are carried by the green cables in the left figure above, are connected to two different INPUTs of QD1 (left). The OUTPUTs from QD1 are shown in the red and cyan (yellow and green) circles for the top (bottom) PMT (center). For the top (bottom) PMT, connect the QD1 OUTPUT highlighted by the cyan (green) circle to the INPUT channel 0 (1) of the counter (right).

Outputs from the PMTs, carried by the green cables, to the INPUTs of QD1.
OUTPUTs from QD1 corresponding to the top (red and cyan) and bottom PMTs (yellow and green).
Two OUTPUTs from QD1 to the counter.

The other QD1 OUTPUT, highlighted by the red (yellow) circle, from the top (bottom) PMT connects to INPUT A (B) of the 4-fold logic unit (left). In same figure (left), we can see the OUTPUTs from the logic unit highlighted in brown and white. The logic unit plays a key role in determining whether a coincidence has occurred which we will talk about later. The white OUTPUT goes to INPUT channel 0 of a second counter (right).

OUTPUTs from QD1 to the 4-fold logic unit.
One of the OUTPUTs from the 4-fold logic unit to the second counter.

The brown OUTPUT from the logic unit goes to the INPUT of the LvL adapter (left). The OUTPUT from the LvL adapter, shown in pink, is then connected to the External Trigger of the DRS4 (right).

OUTPUT from 4-fold logic unit to the INPUT of the LvL adapter.
OUTPUT from the LvL adapter to the External Trigger of the DRS4.

Other Connections on the Hyperdrive Rack
The three components on the hyperdrive rack important to our test are HV (cyan), NIM crate (magenta), and HV Zener divider (green) (left). It is hard to see from the figure, but this is the current order of the components on the NIM crate: QD1, QD2, LvL adapter, and 4 fold-logic unit. Make sure to plug in the cable from the back of the NIM crate to the side of the hyperdrive rack (center). Plug in the cable from the back of the HV to the side of the hyperdrive rack (right).

Hyperdrive rack with HV, NIM crate, and HV divider highlighted in colored circles.
Connection from the NIM crate to the hyperdrive rack.
Connection from the HV to the hyperdrive rack.

There is a thick black cable from the hyperdrive rack that can be found at the bottom of the rack. Plug the cable into a wall outlet (left). Turn on the NIM crate (center) and turn on the HV (right) by flipping the switches (red circles) upward.

Connection from the hyperdrive rack to a wall outlet.
On/off switch for the NIM crate.
On/off switch for the HV.

From the back of the HV (left), connect a cable (cyan circle) to the -HV INPUT of the HV Zener divider (right).

Back view of the HV.
Connection from the HV to the -HV INPUT of the HV divider.

Equipment Settings

Below descriptions of the settings are images of the instruments that show the settings. The parentheses next to the instruments indicate the locations of the images. See the manuals for some of the instruments here.

  1. Pulse Generator (top left)
    1. PULSE PERIOD (s): .1m - 10m
    2. PULSE DELAY (s): 32n - 1μ
    3. PULSE: NORM
    4. PULSE WIDTH (s): 10n - 1μ
    5. Last Column
      1. AMPLITUDE (V): 4.0-10.0
      2. OFFSET: OFF
      4. INT. LOAD: OUT
    6. Vernier: See figure below.
  2. Tektronix Power Supply (top middle)
    1. OUT3: 6.00V
  3. KEITHLEY Power Supply (top right)
    1. Vsrc: 0.0546kV
  4. HV Zener Divider (bottom left)
      1. Column 1: 160
      2. Column 4: 60
  5. HV (bottom middle)
    1. KV/MA: KV
  1. 4-Fold Logic Unit (bottom right)
    1. LED Calibration
      1. OFF: D
      2. Storage for Programming Pins (white strip): should have 2 pins left. Positions of these pins do not matter. This is just a place to store the pins not in use.
      3. COINC. LEVEL: 1
    2. Cosmic Ray Test
      1. OFF: C
      2. Storage for Programming Pins: Same as above
      3. COINC. LEVEL: 2

Set PulseGen.jpeg
Settings on Pulse Generator
Set 6V.jpeg
Settings on Tektronix Power Supply.
Set Vbias.jpeg
Settings on KEITHLEY Power Supply.

Set HV Divider.jpeg
Settings on HV divider.
Set HV.jpeg
Settings on HV.
Set Logic.jpeg
Settings on 4-Fold Logic Unit.

SiPM Apparatus

The SiPM apparatus consists of five parts: top plastic piece, bottom plastic piece, SiPM Chip and SiPM board, and a wrapped tile. A picture of the SiPM chip (circled in read) and the SiPM board (the entire green electronic board) is shown in the figure below. The two plastic pieces are identical except that the top piece has four additional holes for screws. These screws hold the SiPM a fixed distance away from the tile so that the position of the SiPM in each tile's dimple is consistent.

SiPM chip, which is the little square component circled in red, and the SiPM board.

How to Wrap a Tile in ESR

ESR is a reflective paper that we wrap around a tile to make that light created in the tile mostly gets absorbed by the SiPM instead of escaping the tile. Use this template to wrap a 3x3cm tile. For other tile sizes, remeasure the tile and change the dimensions of the template in a software. This template was created in Inkscape.

  1. Print out the template for the wrapping on a piece of white paper. Make sure in the printing option, you are not scaling the template in any way. The template was create in actual dimensions.
  2. Cut out the template and put the tile on top of the cutout, making sure that the template will fit the tile nicely when wrapped. Otherwise, remake the template.
  3. Tape the template on top of a piece of ESR (see figure below).
  4. Cut around the template using a stencil. Make sure to cut through the ESR underneath the template.
  5. Remove the template from the ESR.
  6. Bend the ESR along the solid lines indicated by the template. Make sure the green layer of the ESR will be the side touching the tile.
  7. Punch a hole in the ESR, so that when the tile is wrapped, you can still see the tile's dimple. (You may have to fold one flap over and punch a hole through that flap and the center of the ESR).
  8. Remove the very thin green layer and transparent layer of protective plastic from the ESR.
  9. Wrap the ESR around the tile and tape down the ESR to make sure the ESR will not come off easily.

ESR template.jpeg
Template for cutting the ESR taped on top of the ESR.

ESR Seal
A wrapped tile looks like the left figure below. We always put an ESR "seal" (center figure below) over the hole to make the effective wrapping hole smaller. After putting the seal over the wrapped tile, we get something like the right figure.

A tile wrapped in ESR.
An ESR seal.
A wrapped tile with an ESR seal.

Assembling the SiPM apparatus (SiPM + Board + Tile):
  1. Place the wrapped tile on top of the bottom plastic piece with the dimple in the tile facing the hole in the plastic piece.
  2. Align the center of the tile's dimple with the center of the hole in the plastic piece, with the help of the "X" mark engraved on the plastic piece.
  3. Tape the tile to the plastic piece firmly.
  4. Hold the top and bottom plastic pieces together so that the SiPM is inside the hole of the bottom piece facing the tile's dimple.
  5. Once the pieces are aligned, clamp them together with four paper clips. See figures below.

SiPM apparatus: a combination of the SiPM, board, and the tile. Top view.
SiPM apparatus. Side view.

SiPM and PMTs

Place the SiPM Apparatus in between the two PMTs. Make sure the tile is exactly in between the sensitive parts of the PMTs.

SiPM in between PMTs. Side view.

DRS4 Software

Make sure the DRS4 board is connected to the computer. Open the software. The interface may look something like this (see figure below). If you do not see all the features shown in the figure, here's what you do, starting from the top of the right side bar:

  1. Select "Normal" for the Type of Trigger.
  2. Next to "Normal" make sure the "slope" button is showing a downward slope.
  3. Click on CFG, under Trigger Logic under EXT check OR and Trigger Level to 0.000 V. Do not check other boxes. Trigger level for other channels should not matter.
  4. Set Delay to about 399 ns.
  5. Set Horizontal to 100 ns/div
  6. Click on the boxes labeled 1,2,3,4. Make sure they turn blue. (Although we are only collecting data through channel 1, the root converter program only works when all 4 channels are activated).
  7. Set Vertical under Channel 1 to 20 mV. It does not matter for other channels.
  8. Set Cursors A and B to about 505.6 ns/-12.9 mV and 805.8 ns/-10.8 mV respectively.
  9. Click on the Measure button. A window should pop up. In that window, check only Gated Charge under Channel 1. Near the bottom, check Display Statistics, Display Histograms, and Display Indicators. Set to Accumulate 5000 measurements.

You are all set. Feel free to play around with the various settings in the program. It is not absolutely compulsory for you to do everything exactly the same as above, but these are the settings I use.

drs4 main.png
DRS4 program interface after being set up. The histogram display shows a histogram in an LED calibration run.

Running a Test


Tip, idea Turning off the SiPM power supplies (Tektronix and KEITHLEY) completely by pressing the main power button will reset the settings on the power supply. Use the "output" buttons (labeled "on/off") to turn off the power supplies.

For a test run, we always do an LED calibration followed by a tile test. A test run lasts for about 4 hours, and we do 6 runs for each tile. Because the SiPM's performance is temperature dependence, we are hoping that within 4 hours the temperature does not change too drastically. Also, during the run, I always leave the light in the room on. We have made sure the dark box is well covered up to minimize light from the room leaking into the box, but there might still be some light leak. Since it is hard to do anything such as the LED calibration in the dark, I leave the light on during the tile test to make sure the conditions are the same between the LED calibration and tile test.

LED Calibration

The purpose of this calibration is to obtain a conversion factor between ADC voltage, which is what the DRS records, and PE peak number.

  1. Make sure the SiPM apparatus is placed exactly in between the PMTs and close the dark box.
  2. Set the 4-fold logic unit as shown here: OFF - D, COINC LVL - 1.
  3. Open the DRS4 software on the computer. Make sure the software is properly set up.
  4. Make sure all the power supplies are turned off except for the 6V power supply. (Note: We usually keep the +6V Tektronix power supply on all the time. We only turn off KEITHLEY and HV.) Click the Config button at the bottom right. Click on the Execute Voltage Calibration button and Execute Timing Calibration in turn.
  5. If there is a histogram in the histogram display window, click Measure and click Clear in the Measure window. Close the Measure window.
  6. Turn on the pulse generator by clicking the ON/OFF button below LINE.
  7. Turn on the SiPM power supplies.
  8. Click Run at the top right of the DRS program. You should see a histogram with multiple clearly defined peaks in the bottom display. If you do not, then turn down the VERNIER above OUTPUT (+) of the pulse generator. However, as you turn down the VERNIER, you may notice that there are less peaks in the histogram. You want to make sure you have at least a total of 7 peaks in your histogram. Make sure to clear the histogram every time you turn the VERNIER.
  9. Once you are satisfied with the histogram, click File→Save/Save As. A window will pop up. Select "Binary file (*.dat)" for Save as type. The file should be named in the format below:
    LED_calib[run number]_[date]_vsrc5460.dat
    For example, LED_calib1_10082019_vsrc5460.dat. Save 10 000 events.
  10. Once the DRS program has finished saving 10 000 events, open RunGuiInterfaceProgram on the Desktop. Two windows will pop up. In the DRS4 Data Analysis window, click Browser for DRS Binary (.dat) file, another window will pop up. In that pop up window, select hgcalSoT_Arie→radTiles, find the file you just saved, and double click it. Once the program finishes running, you should see a result like below.
  11. Turn off the pulse generator, and to be safe, also unplug the LED cable that connects to OUTPUT (+). If the LED is accidentally turned on during the tile test, the result from the tile test has to be discarded.
  12. Turn off the SiPM power supply.

Tip, idea Do not close the DRS software, because that might reset the software, and you would have to set it up again.

RunGuiInterfaceProgram LEDRun.png
SiPM signal plot for LED calibration test.

Tile Test

  1. Set the 4-fold logic unit as shown here: OFF - C, COINC LVL - 2. (This means, we do not want input from C, which is the pulse generator, and we want an event to be counted as a coincidence when both A AND B fire at the same time. COINC LVL-1 on the other hand would mean record events if A OR B fires)
  2. With the DRS software still open, click the Config button, and click on the Execute Voltage Calibration button and Execute Timing Calibration in turn.
  3. Turn on the HV and SiPM power supply.
  4. In the DRS program, click File→Save/Save As. Select "Binary file (*.dat)" for Save as type. Name the file following this format:
    [number]_[scintillator]_[date]_c[run number]_vsrc5460_seal.dat
    For example, B_Molded7_10182019_c1_vsrc5460_seal.dat. Make sure that in the same run, the LED calibration file has the same run number as the tile test file. Save 130 events. (This means the DRS4 will only save a maximum of 130 events, which take about 4 hours to save. If 4 hours elapse before 130 events are saved, just click Save in the DRS program. Nothing seems to happen, but in fact the DRS4 program has stopped collecting data and saving them in the file.)
  5. Once the DRS program has collected about 4 hours worth of data, save the file, run the RunGuiInterfaceProgram and select the .dat file you just saved. You should get a result that looks like the one below.
  6. Turn off the HV and SiPM power supply.

RunGuiInterfaceProgram NormalRun.png
SiPM signal plot for a tile test.


In a run, you do
  1. LED calibration

Turn off all power supplies (except 6V)→Set logic for LED calibration→Do voltage and timing calibration on DRS4 software→Plug in LED cable to pulse generator→Turn on pulse generator→Turn on SiPM power supply→Run DRS4 for 10 000 events→Save and convert data file→Turn off power supply and pulse generator, and unplug LED cable

  1. Tile test

Set logic for tile test→Do voltage and timing calibration on DRS4 software→Turn on HV and SiPM power supply→Run DRS4 for 130 events/4 hours→Save and convert data file→Turn off HV and SiPM power supply


The RunGuiInterfaceProgram not only displays the SiPM signal plots, but also converts the .dat file to a .root file to be analyzed. If you go to the hgcalSoT_Arie folder shorcut in the Desktop, you should be able to find those .root files that correspond to the .dat files you saved using the DRS program. Copy all the root files (6 LED calibration files and 6 tile test files) in one complete test (6 4-hour runs) to a folder named after the tile. Clone the repository at https://github.com/Keane-Tan/CosmicRayTileTest, and follow the instructions there to analyze the data.

Manuals for Equipment and Software

Tektronix PS2521G

KEITHLEY 2410 SourceMeter

LeCroy 365AL 4-Fold Logic Unit

LeCroy 821 Quad Discriminator


ChinLungTan - 2019-10-28

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Topic revision: r8 - 2019-10-30 - ChinLungTan
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