Catcher Blindness

1
Catcher Blindness
Hideki Morii

• - Contents -
• Blindness caused by prompt gamma
• Is it a problem?
• Methodology to estimate this problem

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Blindness caused by prompt gamma

• To see the effects of prompt g ...
• Coincidence efficiency
• Single count rate
• Total number of detected photoelectron
• and using spectrum of prompt g
• Number of blind modules per microbunch

3
Coincidence efficiency

• Coincidence efficiency of the catcher
• coincidence condition is front gt4pe , sum
  of backing two gt2pe

lower energy (10100MeV)
higher energy (1001000MeV)
4
Single count rate
Number of modules which detect more than 1pe when
one track comes to the catcher system
lower energy (10100MeV)
higher energy (1001000MeV)
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Total number of detected photoelectrons

• Sum of the detected photoelectrons in all modules

lower energy (10100MeV)
higher energy(1001000MeV)
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Number of blind modules caused by prompt

• Multiply the single count rate by the energy
  spectrum of prompt , we can estimate how many
  modules become blind

lower energy (10100MeV)
higher energy(1001000MeV)
energy spectrum of prompt g
7cm spoiler (TN101)
number of hit modules
19.3 modules / m-bunch
8.1 modules / m-bunch
27.4 modules / m-bunch
(catcher total 370modules)
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Methodology to estimate the effect of blindness

• To estimate the effects of blindness ...
• Make hit map by prompt g
• Overlay them on the g event, and estimate the
  efficiency loss

hit map of prompt g
g event map
satisfies coincidence condition
overlay
this cluster is killed
with the same method, we can estimate the
blindness by neutrons
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Summary

• About 10 of catcher module might be blind by the
  prompt g
• Planning to estimate the efficiency loss using
  overlay method

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Extra Current Design (Configuration)
Top View

• Module Size 30 x 30 cm
• Number of Modules 370
• (278 in beam core / 92 outside)
• Pb plate 2mm per each layer
• Z-gap between module 35cm
• Coincidence condition
• gt 4 p.e. in 1st layer (A)
• gt 2 p.e. in 2nd layer (B)

Beam envelop
Line from opp. edge at the end of DV