Re: Kicker test Nr 2

[Michael Barnes <barnes@triumf.ca>]

Hi all,

Sorry I have been in meetings etc all afternoon so just getting around to
reading email. It is good that you confirmed the general area of the
breakdown. Dave's suggestion may, or may not, work depending on the site
of the breakdown --- e.g. if there is a problem with one of the support
HV1 plate ceramics it will not work. However I suspect the most likely
place for the failure is the Fischer connector. Or maybe it is something
as simple as the internal connection (wire) from the plug to the HV1 plate
breaking and dropping down close to the beam pipe. If you have access to
the beam pipe this would be easy to check. In addition, if there is
nothing obvious in the beam pipe, I would suggest disconnecting the wire
from the Fischer socket (inside the beam pipe). Then repeat the HV test,
with the Fischer plug plugged into the socket. If there is breakdown, it
is the plug or socket; if there is no breakdown, the problem lies with the
deflector plates e.g. support ceramics).

Good luck
Mike

> Peter Winter wrote:
>
>> Hi all,
>>
>> we just performed the test Francoise proposed by removing the fisher
>> plug inside cabinet HV1.
>>
>> Our test included the following steps:
>> 1) Switching to a constant high TTL level (DC mode from endless gate
>> generator)
>> 2) Ramping HV2 to see that all red LEDs are ok at 5kV with fisher plug
>> still inside. That confirmed that we have a high TTL
>> 3) We removed the fisher plug and taped it in a safe position on the
>> plastic shelf far away any metal.
>>     - ramping HV2 to 5kV with lower red LEDs ok, the upper were not
>> lightened due to DC mode
>>     - ramping HV1 without current drawn to 5kV on negative polarity,
>> upper red LEDs turned on, no red LED on bottom stack due to DC
>> 4) We then decided to go to the kicking mode (5mus on at 1kHz) in
>> order to also see the red LEDs on the lower stack of cards in HV1.
>>     - ramping HV2 to 5kV with all red LEDs ok (top ones bright, lower
>> faint)
>>     - ramping HV1 to 2.4kV with 001mA, we observed that the red LED on
>> the card DN-13 had NO red light, while all others were on
>> 5) We reconnected the fisher plug with DC mode:
>>    - HV2 ok when ramping up
>>    - HV1 has immediately a rising current of several mA
>>
>> Summarizing:
>> - It seems that the breakdown is somewhere between the fisher plug and
>> the plate
>> - The card DN-13 still has no red light. Since this is en exchanged
>> card, could the problem be connected with the optic fibre?
>> - When we first saw this breakdown we could go up twice to 2kV with no
>> current. Only when the breakdown occured the current remained. Now the
>> situation changed and we immediately see the breakdown current. Does
>> that mean that the breakdown point worsened and became permanent.
>>
>> Waiting for new proposals and conclusions
>> Brendan and Peter
>>
> Brendan and Peter
> Card dn-13 is likely not getting light from the fiber optics. In order
> to turn off a card (and thus get a red led on) there must be light on
> from the fiber optic cable. A quick check on this would be to
> interchange the fiber optics cables between cards dn12 and dn13 and
> apply HV with the fischer connector disconnected. You will likely see
> that the red LED on card dn 12 will not turn on. You will  need to check
> that the faulty fiber optic cable is connected properly at both ends and
> if that doesnt work then replace the fiber optic cable. If you cannot
> repair this fault you will have to run at a lower voltage on HV1
> cabinet. ie: 16/17*12.5kV=11.8kV to protect the remaining 16 cards in
> the stack. (or see Daves email)
>
> RE: fischer connector.
> The short circuit is either external to the tank or internal. You could
> try cleaning the external connection with alcohol and see if it is
> carbonized anywhere. There might be tracking along Anatolies connector
> when it is plugged in, so it should be dismantled and cleaned if
> possible. It that doesnt work you will have to open the tank and check
> inside. The suggestion of Daves to run with the two sets of plates
> coupled together is probably the best plan and you will still need to
> open the tank to air. You will have to disconnect the internal
> connection of the faulty plate from the fischer connector, or you will
> still have a short to ground.
>
> Regards
> Gary
>
>