[Bteam] no joy again: delivering high current, parity quality beam to Hall C

[Geoffrey Krafft]

BTW,

I've also had a horrible thought!
Are we finally seeing some ion
trapping effects? Does the current
"recover" after the beam is off for
awhile?

Geoff

On 1/27/2011 10:18 AM, Geoffrey Krafft wrote:
> Hi All,
>
> I talked to Alicia this morning, and the symptoms
> remind me of some problems we had awhile ago.
> Have we let the beam size in the first injector module
> get out of hand (get too big!)? Are the spots out of the
> unit proper? The deal is that if the beta isn't small at
> the first cavity, the beam size becomes very sensitive to
> RF phase changes.
>
> What else could be changing?
>
> Geoff
>
> On 1/26/2011 11:44 PM, Todd Satogata wrote:
>> The Hall C Qweak beam problem continues even after spending 12h today on
>> injector configuration checks, 5s polling removal, and retuning with the
>> PREx configuration from August. After work by Reza, Alicia, and Mike
>> Spata, we were able to transport 165 uA to the injector dump, but were
>> only able to transport 80-90 uA to Hall C. About an hour later these
>> numbers were down to about 50-60 uA to the injector dump and 20-30 uA
>> to Hall C, with trips in both the injector chicane and hall transport.
>>
>> This means that the "changing the configuration" card did not help, and we
>> should be prepared tomorrow to take the next step, moving forward (or
>> rather reverting) to the 130 kV gun voltage. It's important that we do
>> whatever we can to put ourselves in the position of beam delivery to
>> both halls over the upcoming weekend. We'll have another meeting tomorrow
>> morning after the 8 AM to review further alternatives and review
>> comparisons of injector viewers taken several times during the day on
>> Wednesday.
>>
>> Some items of note:
>>      - 5-pass pathlength looks reasonable
>>      - Fopt out of the injector looks to have some vertical steps later
>>        into the arcs, but injector match into NL looks okay
>>      - Viewer profiles in Hall C have basically the same aspect ratios
>>        as design, but harp scans show beam sizes 150% larger than "good"
>>        values seen before.
>>      - Prebuncher voltage/phase were reliable enough that Joe got good
>>        prebuncher voltage calibration data earlier in the day, so
>>        the prebuncher is likely stable.
>>
>>                                                    -Todd
>>
>> --------------+---------------------------+----------------+------------------
>> Todd Satogata | CASA Group, Jefferson Lab | (757) 269-6281 | satogata at jlab.org
>> --------------+---------------------------+----------------+------------------
>> _______________________________________________
>> Bteam mailing list
>> Bteam at jlab.org
>> https://mailman.jlab.org/mailman/listinfo/bteam
> _______________________________________________
> Bteam mailing list
> Bteam at jlab.org
> https://mailman.jlab.org/mailman/listinfo/bteam