T-618: A project of E320 and LUXE (DESY) probing the LUXE Cherenkov detector concept at FACET-II
Description of the Experiment
The planned experiment aims to measure Compton electrons from the electron laser interactions arriving at the dump table of FACET-II. The prototype is an in-air system consisting of two complementary subsystems: a scintillating screen and camera system in the front and a Cherenkov detector in the back. The screen consists of terbium-doped gadolinium oxysulfide and the sensitive part of the Cherenkov detector includes 32 thin stainless-steel straws and optical fibers which are placed in air on top of Silicon-Photomultipliers.
The goal is to measure the Compton electron energy spectrum in various modes of the detector setup and determine its performance and accuracy under real physics conditions.
Mechanical Setup
In order to probe various detector configurations the Cherenkov detector part is mounted on a three dimensional stage, placed near the beam dump on the dump table, allowing movements into and out of the beam axis, up and down the Compton electron energy spectrum and a rotation around the vertical axis. These modes enable different sensitivities for different parts of the expected electron intensity range. Since 80/20 frames are used the detector can be easily adjusted to geometrical requirements.
The whole detector shown in the picture above (80/20 frames, screws, threaded rods, patch panels, motors, straw setups, cables, etc.) has a maximal dimension of (100 x 60 x 55) mm³ and a weight of 28 kg.
The Active Detector
The sensitive part of the detector consists two identical setups with several components:
- Frame
- Straws
- Electronics Box
- Darkening Shutter
- Fibers
- LED Box
In the following the quantities of only one of the two setups are given.
NOTE: For the June experiment only one setup ("Box0") is mounted. It is placed such that the rotational axis of the straws is in between the two rows of straws.
1) Frame
All components in the setup are mounted on aluminium 80/20 frames and are supported by cable ties, velcro, screws and custom aluminium frames like
- 4 rods with max. 10 mm and min. 5 mm diameter
- 2 plates with (~135 x ~40 x ~8) mm³ each
- 1 electronics box
2) Straws
- Stainless-steel of type
- Produced via piercing method
- Cleaned but unpolished inside
- 3 mm inner diameter
- 0.1 mm wall thickness
- 200 mm long
- 16 straws
- 8 in one row with 1 mm separation
- 2 rows with 15.5 mm spacing
- The Cherenkov light produced inside the straws is reflected to the electronics box at one end of the straws
- Optical fibers are mounted on the opposite side
3) Electronics Box
The electronics box contains a custom PCB with Silicon-Photomultipliers and passive electronics components. The aluminium box is coated in a black, isolating paint and has the dimensions of (~110 x ~60 x ~55) mm³.
Its lid has a specific cutout for allowing the straws and the darkening shutter to be mounted on top of the PCB. Inside the box the PCB is connected to 1 4-pin and 17 1-pin LEMO connectors.
4) Darkening Shutter
The darkening shutter is a 1 mm thick carbon plate which is placed between the PCB and the straws to mechanically cut of any created Cherenkov light. This allows for a background measurement of the detector.
5) Fibers
Optical fibers are mounted on the opposite side of the straws for the LED calibration system.
- The 0.6 mm fibers are coated in a rubber isolation which results in a outer diameter of 2 mm
- One end of the fibers is set in a brass cylinder with 3.6 mm diameter and mounted in the aluminium plate above the straws
- 2 times 9 fibers are bundled together (8 to the straw rows & 1 for reference)
- These two bundles and the two reference fibers are connected to the LED box
6) LED Box
THe LED box mechanically connects the two fiber bundles to one pulsed LED each. The LEDs are connected via two 5 m long, 2-core coaxial cables to the microcontroller box.
Microcontroller Box
The microcontroller box controlles the LEDs for calibration (4 LEDs in total) and a temperature readout from the electronics box. It contains an arduino and several passive components. It is connected via a +24VDC power supply to the power switch at the dump table. Details are described in the Electronics Setup section.
Scintillating Screen
The used screen is of the type DRZ and consists of terbium-doped gadolinium oxysulfide (<Datasheet> ) and has a dimension of 100 x 100 mm² with a thickness of 0.5 mm.
motor | connector | sub-D |
---|---|---|
P1+ | A | 1, white |
P1- | B | 6, brown |
P2+ | C | 2, green |
P2- | D | 7, yellow |
End+ | E | 3, gray |
End+, gnd | F | 4, rose |
End- | G | 8, blue |
End-, gnd | H | 4, red |
Alignement
- Limit switches are placed
- at maximum for x and y
- such that no mechanical obstacles (e.g. darkening shutter) move into beam axis (aka rotational axis) .
Controller
- The used motor controller is Newport XPS-D Motion Controller
- The used drivers are three Newport XPS-DRV01 Stepper Motor Drivers
- The motors are connected to the motor controller MC17 (FKG20-27)
- The IP address of the controller is 172.27.76.58
- For programming the controller:
- Open web interface http://<ip address> and log in
- Go to Stages → Add, remove or edit stages and create new file by duplicating and modifying old ones
- Go to System → Quick configuration and assign the new driver file to the driver channel
- Reboot and wait for Happy Sound
- The following firmware is used:
- XPS:LI20:MC17:M1 → x direction (transversal, into the beam (+x) and out (-x))
- XPS:LI20:MC17:M2 → y direction (vertical, up (+y) and down (-y))
- XPS:LI20:MC17:M3 → r direction (rotation around y, counter-clockwise (+r) and clockwise (-r))
Calibration
- x direction ranges from 0 mm → +229.541 mm 0.002 mm* (software range limit 232 mm)
- y direction ranges from 0 mm → +231.362 mm 0.034 mm* (software range limit 232 mm)
- r direction ranges from 0° → +59.388° 0.024°* (software range limit 60°)
- Straws perpendicular at r = 27° 0.2°**
*Standard deviation over 5 measurements
**Measurement accuracy with a ruler, (114.0
0.5) mm distance from upstream side profile, 180 mm in -x from the rotation axis. This corresponds to an angle of arctan( ) =- Detector frame overlaps dump table: 23.45 cm
- 13.7 cm
- x = -0.5969 m
- y = -0.3060 m
- z = 2017.5895 m
Electronics Setup
Electronics Details
The setup makes use of several custom and self-designed electronics components including
- Silicon-Photomultiplier electronics
- Darkening shutter
- Microcontroller
- Readout electronics
- Scintillating screen
1) Silicon-Photomultiplier Electronics
- Hamamatsu S14160-3015PS s14160-1315ps.pdf
- ~40k pixel with 15 µm pixel size
- 3x3 mm² sensor size
- ~5*10⁵ gain
- Breakdown voltage ~38 V
- SiPMs sit on a self-designed PCB (PCBSchematics.pdf)
- Temperature sensor of type PT1000 (FST08-B-1K0E.pdf)
- Contains passive bias and signal filters
- The PCB is mounted inside the electronics box ("Box0" & "Box1")
- All signal and bias channels are fed out via LEMO00 connectors
- Temperature is connected to a 4-pole LEMO connector
2) Darkening Shutter
In order to move the darkening shutter (see Mechanical Setup) a magnetic switch is attached to the carbon plate. When +12 VDC are applied the shutter is being pulled and the straws are optically disconnected from the SiPMs. The datasheet can be found here DatasheetMagneticSwitch.pdf.
3) Microcontroller
The microcrontroller box contains a self-made PCB holding an Arduino Micro and various analog components (MicrocontrollerSchematics.pdf). It has two purposes:
- SiPM calibration system
- Generating a pulse to control the 4 LEDs inside the 2 LED boxes
- LEDs are blue LEDs (DatasheetBlueLED.pdf) which are mechanically modified to have a flat lens
- Temperature sensor
- Reading the voltage variation over the temperature sensor
- 50 times every 5 s → Mean and standard deviation returned
In order to communicate with the microcontroller over long distances a half-duplex serial communication using TTL is being used. Furthermore, a TTL trigger signal is being generated for a timed readout of pulsed LED signals.
A second microcontroller board is sitting close to a PC to establish a Serial-to-USB interface. It is configured as the following:
- Baudrate: 9600
- Bytesize: 8
- Parity: None
- stopbits: 1
- Commands:
- "T" : Reads back temperature value
- Returns: "T=0.00 0.00 0.00 0.00 "
- With temperature1 std1 temperature2 std2 (left to right)
- If no temperature sensor connected → "T=NaN NaN NaN NaN " returned
- "R=0" : Sets pulser frequency (int value)
- "L=1111" : Binary mask for LED channels → "L=0001" enables LED0 only
- "U=13000" : Sets LED voltage (int value in mV) of LED0 and LED1
- "V=13000" : Sets LED voltage (int value in mV) of LED2 and LED3
- "T" : Reads back temperature value
4) Readout Electronics
For the SiPM signal readout the CAEN VX1742 sampling digitizer (located in FKG20-24) is used.
- 12 bit resolution
- Up to 5 GS/s
- 1024 bit buffer size
- 32 channels
- 2 trigger channels
- TTL or NIM trigger input
- DatasheetCAENVX1742.pdf
The DAQ software is self-programmed in C++ based on this example: https://github.com/samdejong86/CAEN-v1730-DAQ.
5) Scintillating screen
The camera setup is either the existing LFOV system or LUXE's scintillating screen and camera (Basler) which can be positioned before the Cherenkov detector
SiPM Power Supply
The SiPMs are powered via the Keysight E36234 from the electronics rack (FKG20-24) via a long BNC cable to the dump table.
- 2 channels
- 0 to 60VDC
- ~5mVPP ripple noise
- Usage here: 1 channel with 36VDC to 45VDC
Signal Cables
Section | Type | Length / m | Amount |
---|---|---|---|
Electronics box → LEMO patch panel | LEMO00 | 1 | 18 |
LEMO patch panel → BNC patch panel | LEMO00 | 1 | 18 |
BNC patch panel → E320 patch panel* | BNC | 6 | 17 |
Microcontroller box → E320 patch panel | BNC/LEMO | 1.6 | 2 |
E320 patch pannel → Gallery patch panel** | BNC | ~40 | 19 |
Gallery patch pannel → MCX patch cable | BNC/LEMO00 | 1.5 | 16 |
MCX patch cable → Digitizer | LEMO00/MCX | 0.5*** | 16 |
Electronics box → Microcontroller box (temperature sensor) | LEMO (4-core) | 5 | 2 |
LED box → Microcontroller box (LED pulse) | LEMO (2-core) | 5 | 4 |
*E320 patch panel has common ground!
**Gallery patch panel (FKG20-24) has common ground!
***Cables ch07&15 are 48cm longer!
Trigger Logic
The NIM pulse width of discriminator outputs is set to 10 ns by default. By tuning the first discriminator one can change the pulse timing at the OR input. The final NIM trigger pulse is 50 ns long. With default settings the NIM trigger arrives at the digitizer ~60 ns after the actual trigger input.
The beam trigger is received at the VME crate in FKG20-24:
This trigger can be controlled in facethome:
- Experiment LI20
- FKG20-24 level 35
- Triggers
- Front panel → No 2
Readout and DAQ
EPICS
- to find process variables:
$ eget -ts ds -a name ACSW:LI20:NW06:13%
eget -ts ds -a name
is the command to searchACSW:LI20:NW06:13
is the known part%
is the wildcard
- the other (slower) option is
$ findpv ACSW:LI20:NW06:13%
FACET DAQ
- can be started via: facethome → Physics Apps... → FACET DAQ
- scan functions are saved in: /usr/local/facet/tools/matlabTNG/F2_DAQ/scanFunc_XYZ.m
- an example scan for the vertical position scan is: scanFunc_luxe320_Y.m
- darkening of the SiPM can probably not be scanned since it uses two EPICS addresses (POWERON and POWEROFF)
Computer
- gateway computer flaci@cpu-li20-sp01, accessible from mcclogin, facet-srv*, or thinsrv01
- digitizer computer luxelab@192.168.0.2 (in FKG20-24), accessible only from cpu-li20-sp01 (in FKG20-01)
- ssh flaci@cpu-li-sp01
- ssh luxelab@192.168.0.2
Setup the Tunnel between luxelab and facet-srv20
- set up the SSH tunnel between the luxelab computer and the facet-srv20 we use the following command:
- [fphysics@facet-srv20 ~/ivoschul ]$ ssh -F .ssh/config -N -f luxelab
- -F defines the config file which is not at the default location, it defines
- the users, key-pair, IPs, and proxyjump
- RemoteForward 62882 localhost:62882
- LocalForward 62883 localhost:62883
- -N makes the session non-interactive
- -f puts the session in the background
- to kill the session we can use the following:
[fphysics@facet-srv20 ~/ivoschul ]$ ps aux | grep 'ssh -F .ssh/config'
- this will output three processes, one is the grep command and two are the ssh connections to the gate and to the luxelab
- get the process ID of the connection to the gate and kill it with [fphysics@facet-srv20 ~/ivoschul ]$ kill processID
- port usage:
- 62884 → Ivo's jupyter server on facet-srv20
- 62885 → daq server on luxelab
- 62886 → Antonio's jupyter server on luxelab
Machine/Beam Trigger
- open facethome (from the control network)
- navigate to the Experiment - LI20 section
- select the Triggers... menu in the FKG20-24 section
- our trigger is channel 2 in the front panel section, called trigger FP2
- we use the following settings
- beam trigger (coming from trigger RP2)
- normal polarity
- 1000 ns width
- 10 ns delay
AC Power Switch
- ACSW:LI20:NW06:13XXX
- ACSW:LI20:NW06:14XXX
- ACSW:LI20:NW06:15XXX
Time schedule and planning
Pre-PAMM
- Fix EPICS motor control
- Create power switch (darkening) control
- Ivo Schulthess Create temperature logger control
- Test detector movements
- Test setup with LED
- Remove box1 (and cabling of it)
- Antonios Athanassiadis Documentation of commissioning
- Straw alignment with respect to rotation axis
- Count signal cables
PAMM 06/04
- Turn of XPS controller
- Bring detector into tunnel
- Align detector on optical table (make notes!!!)
- Connect and test motor controller
- Define detectors parking position
- Connect and test power switches for darkening
- Place, connect, and test the arduino (above table?)
- Connect trigger, communication, and signal cables
- E320 patch panel has common ground?
- Measure motor position for being in the beam
- Measure distance beam window to straws/rotational axis
- Set up trigger delays
- Test setup with LED
- Selfie with detector
- Foto Arduino front panel
- One fiber calibration
- LED Voltage/SiPM gain scan
- fight for PP-06 J16 and Spencers channel
Post-PAMM (Pre-Beamtime)
- Write EPICS / CAEN communication
- Create runlist planning
- Test CAEN saving on stop
- Test CAEN saving every N event
- Create main control script
- Extend quickDraw script
- Tidy up computer, put everything in one directory
- ctrl-C proper disconnect
- Update trigger scheme