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[Carl Gagliardi <c-gagliardi AT tamu.edu>]

Hi Elke—

 

As I said during the call, I hadn’t expected that C-AD could take the per bunch current down as low as 1 x 10^{10} per bunch without running into machine instabilities.  So I wanted to check how many bunches would be needed.  Here’s my arithmetic:

 

1 x 10^{10}/bunch is 1/20 of nominal.  I presume this translates into reducing the collision rate by a factor of 1/400.  For a nominal 4+/- MHz NSD collision rate, that corresponds to 10 kHz.  For a nominal 400+/- kHz ZDC rate, that corresponds to 1 kHz.  These are the total rates I proposed, but spread over 100 active bunches, instead of 6.  Thus, the number of collisions per bunch crossing would be ~0.1%, which is smaller than it needs to be.  (Other systematics will be much bigger than that.)

 

Having a modest gap between the active bunches can be useful when looking at the scaler rates.  Thus, I think a good “compromise” would be:

 

2 x 10^{10}/ bunch with a 28 bunch fill.  This should give four times as many collisions per bunch (but still only ~0.5%/bunch) with 1/4 as many bunches.  The total rates should be as above, and should be plenty to saturate the DAQ system bandwidth without producing undo pile up.  Overall, this would be a better optimization than a 6 bunch fill with higher currents per bunch.

 

Hope this is clear!

Carl

 

 

From: Aschenauer Elke-Caroline <elke AT bnl.gov>
Sent: Monday, January 17, 2022 10:49 AM
To: STAR sTGC upgrade <star-stgc-l AT lists.bnl.gov>; Star-fst L <star-fst-l AT lists.bnl.gov>; Carl Gagliardi <c-gagliardi AT tamu.edu>; Flemming Videbaek <videbaek AT bnl.gov>; Van Buren, Gene <gene AT bnl.gov>
Cc: Aschenauer Elke-Caroline <elke AT bnl.gov>
Subject: Re: low luminosity running

 

Based on the input I received I complied the following slides to be discussed today in the trigger-board meeting. Sent me comments by 12:45 pm Thanks elke ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ZjQcmQRYFpfptBannerStart

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Based on the input I received I complied the following slides to be discussed today in the trigger-board meeting.

Sent me comments by 12:45 pm

 

Thanks elke