Last Updated on Thursday, July 26, 2001 at 13:26:19. by Author: David Hofman

BaF2 Monitoring, General Information/Help

(Expert)

Contents

• Description of the BaF2 test setup
  • Overview of the BaF2 test setup
  • Electronics Details
  • Operations
  • Checklist Instructions
  • Trouble Shooter
• How to contact author

Description of the BaF2 test setup

I. Overview of BaF2 test setup

The BaF2 test setup consists of 4 BaF2 crystals (5x5 cm² square area by 25 cm in length) arranged in one small pack. A silicon veto module of type M4T4004 covers the bottom two detectors (number 3 and 4). The purpose of this small test setup is to evaluate the suitability of this type of detector configuration for measuring electromagnetic probes at RHIC energies (i.e. gamma-rays, electrons and positrons).

II. Electronics Details

The silicon veto module is plugged into FEC #26 Port #3. At present it is being given bias voltage and is read out, but is not mapped to a sensor.

The BaF2 crystals are read out by Electron tubes - Thorn EMI 9954-QSB 2" quartz photomultiplier tubes. Bases are of a passive surface mount resistor type purchased directly from Electron tubes. Detector 1 has Voltage Divider type C638B, a tapered distribution divider, and detectors 2-4 have type C638A, a linear distribution voltage divider.

Placement of the BaF2 test array was next to the forward TOF wall, on the side towards the beam pipe. The distance to the BaF2 crystals is slightly longer than to the TOF wall, with the silicon veto module mounted directly in front of the crystals.

High voltage and energy signals were read through extra TOF cabling which the TOF group had already installed.

Energy Cabling

Time Cabling

High Voltage Cabling

III. Operations

1. The high voltage is controlled manually using a LeCroy 4032A power supply mounted in the PHOBOS electronics room, third rack from the left, near the bottom, labeled with a red label as BAF2 HV SUPPLY

2. High voltage to the unit should always be on. This can be seen easily seen by looking at the square status light. The lower half of this square button (labeled as "push for panic off" button) is a yellow Ready light which is always on if the key of the power supply is enabled. The upper half of this switch has the light which indicates the status of the High Voltage. This red light will say HV-ON if the high voltage is enabled and will be off if high voltage is off.

3. If the high voltage is not on, it can be turned on by pressing the "hv on" button. This button is smaller than the square status light button and is located to the right.

4. Only channels 0-3 are enabled. Voltage settings are in channel 0-3 to the values in the table above. This is saved in memory, it will automatically ramp to these preset values when the HV is turned on. All other channels are set to zero voltage so only the first 4 channels will ramp up when high voltage is enabled.

5. The HV can be turned off if needed at any time by simply pressing the "hv off" button. This button is located to the right of the smaller "hv on" button detailed above in item 3. Voltage settings are remembered, so pressing "hv-on" restores the correct values.

6. If there are any problems, simply turn off the high voltage, note in the log book and contact David Hofman.

7. Local (on-site) experts are Edmundo and Rachid.

IV. Checklist Instructions

Either look through window into electronics area or enter physically and look to see current status of the High Voltage power supply. Note the status of the supply as indicated by the lights in the large square button on the front and check the appropriate boxes in the checklist. The usual status should be with "HV-ON" (the red light) and "Ready" (the yellow light) both illuminated.

V. Trouble Shooter

This section is designed for constant additions as problems develop and are solved. If any original problem occurs, it should be noted in this section for future reference.