Si + MCM Assembly QA with an LED

Look here for some history of this QA procedure.

Look here for a few details on the setup.

The QA procedure with the LED

1. Carefully put the assembly on the detector mount on the platform of the x-y table and connect the MCM output cable to the J6 of the power/comm board. Be sure to wear a ground strap and use a vacuum pen to pick up the Si-strip part.

2. Slide in the conductive rubber under the small (bias) pad on the kapton cable from the Si to the MCM, on the left side. Gently squeeze the kapton cable and the conductive rubber against the copper surface of the detector mount with a small clamp. Screw down the Si detector on the detector mount. The result is a Si-bias connection through the conductive rubber and the surface of detector mount.

3. Turn on the stepper motor controller and position the LED above the center of the Si detector (as close as you can).

4. Shield the whole setup by carefully covering the assembly with a black cloth or two and closing the top of the steel box.

5. Turn on everything.
   
   • motherboard and MCM: from the 4 Lambda model LQ-411 (brown) low voltage supplies near the MCM test station.
   • Si bias : From a stand alone supply (Keithley 487) in the rack next to the LED/laser test station. Don't forget to push "operate" to turn it on, then slowly raise the bias voltage to +35Volts.
   • MCM test board : ~6.0V from a (brand?) supply under the laser station
   • NIM crate : used to handle the LVL-1 delay and associated trigger electronics.
   • stepping motor controller (if not done already)

6. Start MCM control software (pcb_mcm, mcm_read, mvd_main) on mvdonl5 (a Pentium-PC for the assembly QA). The easiest way to do this is to start mvd_main and then run the "control.txt" script. Look here for details if you are not sure how to do this.
   • Issue a LVL-1 from the pcb_mcm control panel and make sure the mcm_read control panel responds to the event. [If the power has been cycled, the LVL-1 must be preceeded by a RESET on the MCM_READ panel.]
   • On the scope, you should also see a step pulse on the preamp spy channel with a rise time of ~200ns. A rise time of ~200msec indicated a bad bias voltage connection.
   • Dead channels: verify that all channels are 'on': in PCB_MCM, EDIT, check all 8 TGV groups, set all PREamp DISable bits to 0. Then set known bad channels to 1, using the assembly info sheet, channels listed under (#0-#255 MCM). Don't forget to do a SEND after you checked and set the dead channels.

7. In the Mcm_read control panel, click on "LED Test". This pops up the the LED test control panel. Then do the following:
   • Put the name of the assembly (e.g. IB-04) in the "assembly name" box
   • Set the number of events in the box labeled "events" -- 100 is enough but use more (say 1000) if you have time.
   • Push the "stop" button on the LeCroy 222 gate generator in the NIM crate labeled "LED on/off". The red light should be off. This disables the LED.
   • click on "start LED off events" and wait for all the events to be read (the current program is too stupid to wait by itself)
   • click on "LED off finished" when all the events are completed
   • Push the "start" button on the LeCroy 222 gate generator in the NIM crate labeled "LED on/off". The red light should be "on". This enables the LED.
   • click on "start LED on events" and wait for all the events to be read
   • click on the "LED on finished" button
   • click on "Calculate". This button causes a file to be written which summarizes the results (sample file here). It also draws a plot of the response to the LED vs. ADC channel number and writes the number of bad channels and a few other details onto the control panel.
   • Record the number of bad channels, the average difference, abd sigma.

8. There should be a file called c:\mvd\histos\led_[assembly name].dat created, where [assembly name] is something like OB-04.

9. Power down before you open up the box: the 4 Lambda units, the Keithly-487, the supply under the laser station.

10. If you want to move the xy table, the buttons on the front panel are the easiest way when the light box is open. If you want to adjust the positions of the LEDs during the tests, look here for some instructions.

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    last update: 4-Jan-2001
    John Sullivan (sullivan@lanl.gov) & HvH

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