(Manual is refering to May06)

Operating

Please read "Understanding" first!

HV is found in Epics under PION HV.
Only the first four channels in HV card 1,2,3 are used for Fiber Start. Card 1 is main HV, card 2 is Dyn9, card 3 is Dyn10.
Dyn11 and Dyn12 are put to Wolfgangs Low Voltage system.
Important! Readback values from epics seem to be wrong by 5%.
Numbers given in this manual correspond to the actual readback value!

Ramping up

• Ramp up card 3 to 300V
• Ramp up card 2 to 75
• Ramp up card 1 to 75
• Ramp up card 2 to 150
• Ramp up card 1 to 150
• Ramp up card 2 to 220
• Ramp up card 1 to 220 (Maximum!). Setting to 2000 will result on 220V output.
• Ramp up card 2 to 290 (Maximum!). Setting to 2000 will result on 290V output.
• Ramp up card 3 to 900. Setting to 2500 will result on 900V output.
• Now switch on the LowVoltage with the Web interface.

Ramping down

Basically the other way around.

• Switch off the LowVoltage with the Web interface.
• Ramp dowm card 3 to 300
• Ramp dowm card 2 to 225
• Ramp dowm card 1 to 150
• Ramp dowm card 2 to 150
• Ramp dowm card 1 to 75
• Ramp dowm card 2 to 75
• Ramp dowm card 1 to 0
• Ramp dowm card 2 to 0
• Set card 3 to 0V

Do not switch of the Crate, because Veto and Tofino are also in there!!!

External access to Low Voltage

Use any webbrowser to access http://haepc04.gsi.de. Click on login. Username is (i wont put the password here). Ask! Switch on/off ONLY PionLowVoltage.

Understanding

Booster base

The Hamamatsu PMTs use a passive voltage divider. What happens if you have high rates (and big signals) is that the voltage breaks down on the last few dynodes. Amplification which change with rate.

To work around that problem, we attach independent supply on the last dynodes. But this leads to the problem that the voltage between dynodes must be carefully controlled. Which is hard if you cannot trust the HV crate slowcontrol!

"Low" Voltage

Self-built 75V/150V system, which can only be turned on and off (no ramping).

(developed by W.Koenig)

"High" Voltage

Normal LeCroy HV cards with modified HV limits. These limits are set by HARDWARE and cannot be overwritten by software. This leads to some interesting effects... like red bullets in epics even if everything is O.K.

Operating

Never never NEVER have more that 80V difference between two neighbouring dynodes!!!

Effect of HV limits:

• dont be scary about the red buttons, thats normal. the boards cannot set the user value because they are limited by hardware. this results in the red signs.

• example: Fiber Hodo HV with limits: (click for full view)
  

-- BjoernSpruck - 31 Mar 2006