[Hps] HPS is taking data

[Maruyama, Takashi]

We thought about several possibilities such as bleedthrough beam, multiple scattered beam electron but Stepan came up with the bremsstrahlung explanation.  The vacuum in downstream of Tagger magnet is about 5x10^-4 Torr. Beam electrons emit brems photons in beam gas interactions. Lower energy electron are bent more by Frascati magnet. The flange for the PS vac chamber is from our test run and has 3" hole. The nominal beam is only 7 mm from the flange edgge when the chicane magnet is turned on. The brems degraded electron will hit the flange and generate brems photons which hit the ecal near the photon line. 

  Takashi
________________________________________
From: Maurik Holtrop <maurik.holtrop at gmail.com>
Sent: Saturday, December 13, 2014 8:05 AM
To: Maruyama, Takashi
Cc: HPS
Subject: Re: [Hps] HPS is taking data

Hello Takashi, Stepan and all of you on shift,

This is really great!

I went through the logbook entries and don't see the entry that explains what the source of background was and how it was eliminated. If you have a moment, could you please point me to the right entry? Was it beam-gas interactions?

Best,
        Maurik


On Dec 12, 2014, at 8:39 PM, Maruyama, Takashi <tvm at slac.stanford.edu> wrote:

>
> With heroic effort by Stepan, the anomalous source of background was identified and eliminated completely. 1.5 micron-thick Pt target was inserted. Attached is a ECal single rate map at 10 nA. This is very similar to what you see in Monte Carlo.
>
> Ben has setup a very loose two cluster trigger and Sergey's DAQ system is taking data at 4.5 kHz at 10 nA. This data will be used to find optimum cuts for pair trigger.
>
> Takashi
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