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After the detectors have been received, they have to be cooled to LN₂ temperatures and powered up before testing.

[edit] Pre-Cooling

First, it is important to make sure that the bias shutdown circuit (BSD) is working. When the preamp power is on, the two pins of the BSD connector will either make a short or open circuit. A preamp power CPC pigtail can be used for convenience. Pins 4 and 6 on the CPC connector are connected to the BSD. If there is an open circuit, then the detector is warm (this is a fault when operational). If there is a short circuit, the detector is at the required LN₂ temperature.

[edit] Cooling

In order to cool the detector, you need to unscrew the plug on the top and insert the fill tube. The first fills will begin to boil off, and filling needs to continue until the dewar overflows. The detector has to be filled every hour for at least two more fills afterwards. All subsequent fillings need to be in 8 hour intervals.

[edit] Pre-Amp Power

The preamp leads go to the left and right side of the clover, between the red/green crystals and the blue/white crystals. They are connected to the "Preamp Power" connectors of the Ortec 855 SpecAmps inside the power crate. After application of preamp power, the detector needs to be left overnight to warm up the electronics before high voltage application.

[edit] High Voltage Application

The high voltage cables are connected to the HT connectors for each crystal. The required voltage is on the sticker beside the high voltage cable, and can also be found in the detector manual.

Once the preamps are warm, it is important to check the signal with zero bias voltage. The scope should have four probes connected to the FV connector for each crystal, and should be set at 20mV and 40µs. The negative slope trigger should be set and the noise is expected to be around 10 mV or less peak to peak. The shutdown box needs to be checked in the case that the detector warms up unexpectedly. In order to do that, the signal cable needs to be disconnected. That should shut down all the High Voltage supplies.

Next, the HV supplies need to be set to zero, if they already are not. It is crucial to ensure that the polarity of the High Voltage supplies is positive. Once all the supplies are at zero and the dials are unlocked, they can be turned on using the ON switch and then reset. Afterwards, the ON light should light up. Voltage increase on the vernier scale is 10-fold and the window above it shows the 1000's scale when the RG6Z HV cable is connected to the 0-5000V rear output of the Ortec 660 HV module.

The oscilloscope needs to be set at 200 mV and 400 µs with the trigger far above the scope window. The signals from the 4 crystals need to be lined up near the bottom of the window. The first voltage increase is from zero to 100 volts. After the increase, the four signal lines will rise to the top of the screen and then slowly settle down. Once that is done, a signal check needs to be done with the scope at 20 mV and 40 µs. It should be noted that the noise needs to be circa 5 mV peak to peak and that the signal to noise ratio is sufficiently high. The scope is then changed back to its biasing mode (200mV, 400µs) and then 200 more volts need to be applied. After waiting for the signals to recede to their nominal value, the voltage is increased again to 500 volts. After that, the increase steps go by 300 volts until the operating voltage is met, remembering to wait after every voltage raise.

[edit] Powering Down

When powering down the detectors, the scope needs to be at the 200mV/400µs specification and all the signals need to be lined up near the top of the window. Drop the voltage by 500V every step and wait until the signals have returned to the top after every voltage drop, until zero volts has been reached. After all the crystals are at 0 volts, the vernier knobs need to be locked. Finally, the shutdown cable needs to be removed and replaced in order to put the HV supplies into shutdown mode.