Primary Proton Plug MC Study

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Primary Proton Plug MC Study

• Joshua Spitz
• Construction meeting 6/30/05

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What does a plug do?

• When JPARC increases from .5MW to 4MW, the beam
  dump may be in trouble.
• High energy protons irradiating the beam dump.
• A graphite cylinder in the beamline will absorb
  some of these primary protons.
• Potential pion absorption at the plug.
• Loss of neutrino flux.

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What I have studied

• MC simulation using JNUBEAM.
• Plug geometry optimization (radius and length).
• Minimizing neutrino flux loss
• Maximizing primary proton absorption
• Figure of meritprotons with Pgt35GeV/c
• Plug position optimization
• Where between horn 2 and 3?
• Parent pion and background creation at plug

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Proton profile without plug in place
At beam dump
P gt 35 GeV/c
P lt 35 GeV/c
About 15.5 of primary protons make it to the
beam dump without a plug in place.
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Basic effect of a plug
2cm radius, 60cm length plug in place
No plug in place
At beam dump
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Basic effect of a plug part 2
At beam dump
2cm radius, 60cm length plug in place
No plug in place
Pgt 35 GeV/c
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Plug geometry optimization

• Proton stopping power has an upper limit in terms
  of plug length.
• Plug radius of 3cm is too large for maintaining
  nu-mu flux.

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Plug geometry optimization part 2
X(top) and Y(bottom) position of protons with
Pgt35GeV/c at beam dump. Black is without plug,
red is with plug. On left plug with 2cm radius,
40cm length. On right plug with 2cm radius,
120cm length. 106 POT.
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Plug geometry optimization part 3

• Geometry optimization was completed with plug
  about halfway in between horn 2 and 3.
• Longer plugs are better.
• Upper limit to plug length, beyond which more
  plug is unnecessary.
• The best plug radius is between 1cm and 2cm.
• Up to 60 primary proton absorption with a plug
  in place with negligible neutrino flux loss.
• Possibly 65-70 primary proton absorption with
  plug very close to downstream horn 2.
• Very low(1) increase in secondary protons.

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Nu-mu and background with a plug

• Why is there no loss in neutrino flux with a
  1-2cm radius plug?
• Parent pion creation in plug can contribute to as
  much as 2.5 of total nu-mu flux.
• Pion absorptionpion creation
• All background particles increase with a plug in
  place.
• Parent creation at plug.
• Little kaon absorption (compared to pion).
• Kaons often decay before reaching the plug.

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Nu-mu from parent created at plug
Black is total flux. Red is flux from parent
created at plug(2cm radius, 40cm length).
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Background and the plug

• Kaon absorption in plug is not high since kaons
  may decay before reaching the plug.
• In plug, kaon creation is greater than kaon
  absorption.

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Plug position

• Most of this study was completed with the plug
  about half way between horn 2 and 3.
• However, basic simulations were completed to
  study the optimal position of a plug.
• A plug as close as possible to downstream of horn
  2 is best for proton absorption.
• Neutrino flux does not suffer.
• Primary proton cone is smaller.
• Maximizes proton absorption.

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Nu-mu-bar beam and the plug

• Nu-mu is a large background source for a
  nu-mu-bar beam.
• With a plug in place, the nu-mu background will
  increase by 10-15 (depending on radius and
  length).

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Plug advantages/disadvantages

• Advantages
• upwards of 65 primary proton stopping power
• zero neutrino flux loss
• Disadvantages
• increase in background rates
• 5 increase in nu-e flux.
• Larger increases for nu-bar background.
• increase in background rates with nu-mu-bar beam
• 10-15 increase in background nu-mu flux