PI > Sebastian Bachmann > LHCb

High voltage tests with the LHCb Outer Tracking system

The high voltage distribution for the LHCb Outer Tracking System is described in detail on the LHCb home page (see at OT Electronics->HV distribution->Overview). The mapping between the CAEN power supply and the channels for each FE-box is also described there.
The table given below shows the currents during ramping voltages and the dark currents with high voltage applied during the burn-in of the detector modules. During th burn-in procedure the detectors are supplied with the counting gas (Ar/CO₂ 70/30) provided by the final gas system. The ramping procedure for the high voltage is the following:

Go to status standby 1 (ramping_standby1).
Keep status standby 1 for a few minutes. Check that all currents are below 500nA.
Go to status standby 2 (ramping_standby1).
Keep status standby 2 for a few minutes. Check that all currents are still below 500nA
Go to status ready.

The parameters used are:

Maximum voltage (by software): 1600V
Ramp down speed: 40V/s

and the parameters for the different status:

Standby 1: U=20V, I_max = 5�A, ramp up speed: 2V/s
Standby 2: U=1200V, I_max = 2�A, ramp up speed: 5V/s
Ready: U=1550V, I_max = 2�A, ramp up speed: 5V/s

Here is the table with the measured current: Burnin.xls
The currents are given in nA. When a value is not filled the channel has not yet done the burn-in test.