Disc Services Testing in Testbox

Thermistor Check

Check both NTC's of the dummy modules give sensible readings.
(Implies Select and Temp lines are connected)

HV Check

Check current flows while ramping voltage up
(Implies BIAS and BIASRETURN are connected)
Check current is zero when high voltage is 500 V
(Implies no leakage in services)

Diode check


Set pin-bias to 6 V with no light on, and check no-current
Shine light on diode via BOC, and check there is a current
(Implies diode is not broken, is connected electrically, and fibres are OK)

VCSEL check


Set ILED to 6 V
Check VCSEL current is normal
(Implies VCSEL is OK and ILED line is connected)
Disconnect test fibre at BOC and check light is reaching BOC. However, only do this if you suspect a problem, since there is a risk of damaging the RX piggy-back in the BOC.

Over-pressure check

Make sure disc is connected to circuits correctly, and relevant valves in test-box are open.
Close the disc test box door for safety
Introduce nitrogen into the lines to 20.5 bar absolute. Do this in stages and check no large leaks appear at any stage.
If nothing breaks and no major leaks appear, the over-pressure test is complete and the door can be opened again.

Leak check


Pressurise the disc cooling circuits with nitrogen to about 20 bar absolute
Close the test-box outlet valve V13
Close the inlet valves in the test-box
Monitor the pressure in the outlet manifold for 24 hours
Calculate the (temperature corrected) leak rate, and then scale it to what it would be at 2 bar
Check that total leak rate - test-box circuit leak rate  <  no. circuits * 5x10-4 mbar l / s (ref. ATL-IS-ES-0069).

...Implies the circuits and PPF0c connectors have a low enough leak rate for ATLAS

Power lines and cooling check

  1. Fill the lines with C3F8 and turn the cooling on (see cooling plant instructions)
  2. Set needle valves to correct flow
  3. Turn the power on (Vcc and Vdd)
  4. Check sense wires are OK via SCTLV Power Supply DCS screen (ask Auke how)
  5. Check Icc and Idd are appropriate for a 5 Ohm resistor
  6. Check NTC's on cooling circuits: exhaust temperature should be lower than inlet temperature for evaporative cooling
  7. Check NTC's on dummy modules...allowing for main or secondary block, or inner module NTC1 or NTC2; and allowing for high low blocks and actual power in the heaters...check no major excursions from the expected values.
...Implies coolant flow is sufficient, cooling blocks are correctly coupled to pipe.
...Implies all power lines and sense wires are OK

Thermal Cycle

Cool down the disc to -25 degC
Warm up to +20 deg C
Repeat 5 times

...needs study how to do this. Do we have dummy modules powered? Do we use them to warm up the box? Do we need a heater in the box? Computer control to do things gradually and without tripping the compressor (over-heating) will make life easier.

Reset Line

The above procedures test all wiggly tape lines except the reset. I could not find an easy way to test that with a dummy module. But (i) it was tested many times during services to disc assembly (ii) it is the least important line on a wiggly (we can issue soft resets or power cycle a module) so I do not think it is a big problem to leave it untested. If there is a reason to suspect it, then test it by disconnecting the test cable at TPPF1-C and measuring the resistance between Reset and DGND ...should be  close to zero Ohms.

 
Nigel Hessey 7 April 2005