[Primexd] [Revised Logentry] CCAL (NPS prototype) beam scan

[somov at jlab.org]

Logentry Text:
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We moved each CCAL module to the beam and collected data for calibration and detector resolution studies.
Data were taken for different HV values.

For most  CCAL modules, we'll need to set HVs to the relatively small value below 700 V.

Fig. 1  - Fig 5 show the CCAL fadc peak amplitudes as a function of the TAGH counter (energy).  
Saturation of FADC amplitudes  (the maximum fadc range is 4096 counts) at high voltages  
can be seen on Fig. 1 (for 680 v)

Note, we also had to set HVs to the relatively small value during the beam test of the 3x3 prototype, 
which we performed with Vlad in Spring 2018, see

https://logbooks.jlab.org/entry/3563789

We are going to check energy linearity using recorded data 
(operating CCAL at small voltages may no be a concern, but the gain of 
the on-board amplifier (on the divider PCB) should be reduced for the future FCAL II 
insert. 

We may consider to slightly increased HVs by switching the fadc amplitude 
range to 2 V (the current setting is 1 V) after performing CCAL rate studies. 
Note, the PMT gain  "drops" at smaller voltages for larger anode current 
(pulse amplitudes).

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Fig. 6 FADC peak amplitudes corresponding to the photon beam energy of 
about 4.1 GeV (TAGH counters 243) for different HV settings ( CCAL module 4, -5 ).
Dependence of the CCAL amplitude on HV was fit to the power function.


Fig. 7 The same as in Fig. 6 for the CCAL module (2, 2) from the 
inner most layer covered by the Tungsten absorber. The beam goes
through a 5 mm absorber hole in the middle of the module.






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This is a plain text email for clients that cannot display HTML.  The full logentry can be found online at https://logbooks.jlab.org/entry/3633958
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