Equipment Operation Instructions

Laser setup

Probe Station


Alibava is a readout system for micro strip detectors, named after the institutions that developed it: Liverpool. Barcelona, and Valencia. At Birmingham, as of August 28, 2018, we used the system along with a Sr90 radioactive source to characterize the charge collection efficieny (CCE) of strip detectors.


The system consists of a number of components:

  • Fridge
  • Alibava motherboard
  • Alibava daughterboard
  • Sensor
  • 2 Scintillators coupled to photomultiplier tubes (PMTs) (Scintillator "B" typically gives ~5x more output than Scintillator 1)
  • Fan
  • Temerature and humidity sensors readout by Arduino board
  • Aluminum box to house Alibava daughter board, fans, scintillators and PMTs, and temperature and humidity sensors.
  • High voltage power supply: Keithley 2410) - used for sensor
  • Low voltage power supply: TTI EX354RD - used for scintillators
  • A simple breadboard to control the PMT voltages
  • A 2nd low voltage power supply when the breadboard seems to not work (ideally always use this)
  • Oscilloscope - used to monitor scintillators
  • Sr90 beta source
  • Nitrogen gas source in rhs of fridge (coming out of grey block)
  • Smaller rainbow cable, which monitors temperature and humidity, powers the fan and powers the PMTs in the scintillators
  • Signal cables of oscilloscope
  • Power cables for alibava
  • Cable blocks to replace broken ribbon cable parts (don't worry about purple and grey wires hanging out, they do nothing)
  • Large ribbon cable should always be attached
  • Python script lives at ~/temphum/python_temphum*.py, and outputs data to nohup.out and/or output_temp_hum.txt
  • Aluminum tab to block hole to radiation source

A schematic of the setup is here: alibava_schematic.pptx

Annealing Sensors

  1. ONLY handle sensors with carbon, plastic or vacuum tweezers. NOT metal.
  2. Use oven at back of clean room entrance hallway
  3. Turn on.
  4. 60, 100, 120 and 130 degrees C are marked in pen (60 is just marked with a dot)
  5. Orange HEATER light will run off when the oven is at correct temperature
  6. Add a temperature sensor near the sample in the alibava setup to cross check the oven temperature
  7. Store sensor in small tin foil trays in cardboard box to left of oven.
  8. Sensor is small grey box with T1 and T2 written on it. Can use body temperature to test which is which.
  9. Standard with annealing is 60C for 80 mins.

Data Acquisition Procedure

The procedure to collect data is as follows:

  1. If you are doing a cold run, make sure fridge is set to "super", rather than "stop" or "normal". Knob is on right side.
  2. Outside of the fridge add daughterboard to alibava box, making sure pins go in holes to hold it in place. Make sure nitrogen tube, humidity sensor are attached.
  3. Make sure temperature sensor is in heat sync on the back of the daughterboard (tape it down).
  4. Attach high voltage cable to the daughterboard.
  5. Add alibava box to fridge, making sure hole in lid is below source, and aluminum tab is removed.
  6. Connect nitrogen (on RHS on fridge from grey block) to alibava box, and connect nitrogen source (at wall) to cable going into fridge. The nitrogen should always be connected to the box when it's out of the fridge
  7. Connect smaller ribbon cable, making sure XX marks are on same side. This cable monitors temperature and humidity, powers the fan and powers the PMTs in the scintillators
  8. Make sure power supply is plugged into voltage splitter (or power supply). And all labelled cables are in appropriate places in voltage splitter, or power supply. If you are using the power supply be sure you tie the grounds its terminals to the ground for the PMT circuit.
  9. Plug high voltage power supply for sensor bias in. Cables are labelled as Alibava (or capitalised) HV. Make sure red (HV) is connected to red and black (ground) to black.
  10. Attach cable blocks using a screwdriver, which replace broken ribbon cable parts to power the PMTs. Make sure to follow the lables for "+5V", "Vcont", and "Vref."
  11. Attach the LEMO cables for the PMT signals. Cables are both color coded and labeled.
  12. Close the fridge, including the straps on the side. The only cable in the door of the fridge should be the large ribbon cable (unless we have fixed this). All others should go through the hole in the fridge.
  13. Make sure Arduino board (monitors and reads out temperature and humidity) is connected to the PC via USB, and make sure python script is running (~/temphum/python_temphum*.py). If you see sporadic readings for the temperature and humiity, it is probably due the small ribbon cable being disconnected or connected incorrectly.
  14. Make sure power is connected at wall and turned on.
  15. It is advisable to check for PMT signal on the oscilloscope and make sure you can trigger on settings that are comparable to Alibava, that is a 200mV trigger.
  16. Check the connection from the PC to Alibava by doing a pedestal run. Be sure the DAQ software is not running in emulation mode.
  17. If the above two steps are proving difficult, see trouble shooting.
  18. Connect PMT output the to alibava motherboard. White cable to white strip on motherboard box, and green cable to red strip.
  19. Wait for the temperature to reach approximately -25C. This can take 2-3 hours, but will go faster if the daughterboard and HV supply are turned off as the current flow causes heating.
  20. Bias the sensor by: set compliance to 1 microamp using "EDIT" button, up and down arrows, and then enter.
  21. Put a small bias on the sensor in each direction to check the device polarity. Use which sign of voltage gives the lower current, and apply whatever bias voltage you're testing.
  22. If you have not done so, turn on Alibava.
  23. On the PC, open the program "Alibava" to begin data aquisition.
  24. Do a run in "Pedestal" mode to check that the board and PC can communicate.
  25. Switch to "RS" mode for triggering off a signal from a radioactive source. We typically acquire 100 000 events per bias voltage, which has taken about 8 minurtes a run.
  26. In the settings menu, check that trigger is set to "OR" and that the trigger levels are -200mV.
  27. If you want to collect data, click "Log Data" and write the name of the file you want to save. The current convention, on which the analysis is dependent, is name of the form "RSRun-##C-XXX_###V" where the first ## is the temperature, XXX is the trigger configuration ("OR", "OR-GREEN", or "OR-WHITE"), and the last ### is the bias voltage.
  28. When the run is finished, adjust the bias voltage and start the next run.
  29. When you are done with a sensor for the time being, you must decide to either leave it in the fridge or remove it. If the sensor is irradiated, you will have to keep it cold after heating and removing.
  30. To remove the board and sensor, open the fridge and quickly undo all the connections possible, this should leave only the large ribbon cable. Remove the nitrogen last. Remove the Al box from the fridge and close the fridge door.
  31. Immediately reconnect the nitrogen from a point further upstream in the line to the box. The flow will be faster here, check that it isn't too much for the sake of wire bonds.
  32. Reconnect the small ribbon cable. There is small length identical to the portion in the hole in the fridge, use that. This allows you to have temperature and humidity monitoring for the box outiside of the fridge.
  33. Wait for the temperature to reach the dew point for the ambient air. For ISO7, the humidity is ~50% and temperature 22C, giving a dew point of 11.1C (; 12 C may be safer to guarantee no condensation.
  34. You may now remove the lid of the box to access the contents to replace the sensor or make repairs/adjustments.

To remove the daughterboard from the box in order to, for instance, give the board to a technician (Simon) for wire bonding:

  1. Remove temperature sensor from heat sink
  2. Remove humidity sensor
  3. Disconnect large ribbon cable
  4. Disconnect power supply
  5. Pull nitrogen tube out
  6. If giving to Simon for wire bonding, remove any tape from bottom as it must be level

Trouble shooting

  • If the GUI for data acquitiion isn't working, close the GUI, power cycle Alibava, and open the GUI. This may take a few iterations.
  • If power cycling/rebootinh the GUI and Alibava doesn't work, the problem may be the wire bonds, particularly on either of the Beetle chips, or the large ribbon cables. You can check the wire bonds on the chips visually and the cable with a ohmeter.
  • If scintillators don't work, check power source, Vreference and Vcontrol (Vreference and Vcontrol should be ~1.1V). Check that current from power source is 5 or 6 mA. If it is 2-3mA, then probably only one PMT is working. You can use as oscilloscope to check the signals as well.
  • If you cannot get PMT bias right with the bread board, try using a power supply instead.
  • If you see strange readings in temperature or humidity, check that ribbon cable is connected correctly
  • For the analysis software, close and open software GUI after recompiling software

Safety and Warnings

There are some warnings for the sake of the system:

  • Avoid condensation on the board and sensor. This should not be an issue when cooling down as the ambient air will probably always be cooler than the sensor. However, when heating up, the opposite will be true. Ideally we would have 2 separate sensors, one for the ambient air and the other for the sensor. If we assume some reasonable maximum temperature difference between the two, say 7C, we can calculate the relative humidity at which condensation will begin as in RH_dT7C.xlsx a la As long as we are below 53% RH, we should avoid condensation.
  • Be careful of damaging wire bonds on Alibava. The bonds are on the sensor and the two Beetle chips on the daughterboard. You should be able to spot them with the naked eye, but a microscope can also be helpful. Never allow anything to touch the wire bonds. They will also corrode when wet, anothe complication related to condensation.
  • Never touch sensor (but you can touch the daughter board when the sensor is on it)
  • Ground yourself before touching any electronics (can use metal plate ground point under laser)
  • Note that condensation or frost will gather in fridge when it's turned on with the door open. When it gets too icy, it is good to turn it off, let the ice melt and drain it.
  • Nitrogen should always be connected to Alibava.
  • Keep Alibava box as airtight as possible (mostly using tape).
  • Before opening fridge, turn off power supplies so that nothing gets a large leakage current from light from the room. Also the insulation on the HV line leaves a bit to be desired, staying away from the cables while biased is probably safest.
  • This experiment does involve a radioactive source, please keep your radiation training and the principles of ALARA in mind.

-- Patrick Freeman- 28 Aug 2018

-- LauraGonella - 09 Aug 2018

Topic attachments
I Attachment History Action Size Date Who Comment
Xlsxxlsx RH_dT7C.xlsx r1 manage 38.3 K 28 Aug 2018 - 15:14 UnknownUser Relative humidity at dew point for a 7C temperature difference.
Pptxpptx alibava_schematic.pptx r1 manage 37.4 K 28 Aug 2018 - 16:25 UnknownUser Schematic of Alibava DAQ
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Topic revision: r2 - 28 Aug 2018 - _47C_61UK_47O_61eScience_47OU_61Birmingham_47L_61ParticlePhysics_47CN_61patrick_32freeman?
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