1
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- Providing High-Intensity, Low-Emittance Muon Beams for the Neutrino
Factory and Muon Collider
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2
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- Future Accelerator Projects Requiring Muon Front Ends
- Neutrino Factory
- Muon Collider
- Choice of Particle – why Muons?
- Design Components and Options
- Research Currently Underway
- By both Grahame Rees and myself
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3
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- Goal: To fire a focussed beam of neutrinos through the interior of the
Earth
- Constrains post-Standard Model physics
- But why does this involve muons?
- Neutrinos appear only as decay products
- Decaying an intense, high-speed beam of muons produces collimated
neutrinos
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4
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- p+ à p+
à m+ à e+nenm
- Uses 4-5MW proton driver
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5
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- Goal: to push the energy frontier in the lepton sector after the linear
collider
- p+ à p+,p−
à m+,m−
à
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6
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7
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- Must accelerate muons quickly, before they decay
- Synchrotron acceleration is too slow
- But once g is high, you have more time
- High emittance of pions from the target
- Use an accelerator with a really big aperture?
- Or try beam cooling (emittance reduction)
- In reality, do some of both
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8
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- Targetry, produces pions (p±)
- Pion to muon decay channel
- Uses a series of wide-bore solenoids
- “Phase rotation” systems
- Aim for either low DE or short bunch length
- Muon ionisation cooling (as in “MICE”)
- Expensive components, re-use in cooling ring
- Muon acceleration (RLAs vs. FFAGs)
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9
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- Has to deal with the “beam” coming from the pion source
- Pion half-life is 18ns or 12m at 200MeV
- So make the decay channel about 30m long
- Grahame designed an initial version
- Used S/C solenoids to get a large aperture and high field (3T mostly,
20T around target)
- Needed a better tracking code…
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10
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- Developed a more accurate code
- Used it to validate Grahame’s design…
- 3.1% of the pions/muons were captured
- …and parameter search for the optimum
- Within constraints: <4T field, >0.5m drifts, etc.
- Increased transmission to 9.6%
- Increased in the older code (PARMILA) too
- Fixed a problem in the original design!
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11
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- Chicane (2001)
- FFAG-style magnets
- Shortens the bunch
- Have optimised matching
- No cooling?
- 31.4MHz RF (2003)
- Reduces the energy spread
- Feeds into cooling ring
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12
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- 10-20 turns
- Uses H2(l) or graphite absorbers
- Cooling in all 3 planes
- 16% emittance loss per turn (probably)
- Tracking and optimisation later this year…
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13
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- In case the time is longer than my slides.
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14
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- Accelerators must have a large aperture
- Few turns (or linear) in low energy part, so muons don’t decay
- Recirculating Linacs (RLAs, studied first)
- FFAGs (cyclotron-like devices)
- Grahame is playing with isochronous ones
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15
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- “Success” is 1021 m+/yr in the storage ring
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16
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- Distributed Computing
- ~450GHz of processing power
- Can test millions of designs
- Genetic Algorithms
- Optimisation good up to 137 parameters…
- Accelerator design-range specification language
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17
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- Has to deal with the “beam” coming from the pion source
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18
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- 12 parameters
- Solenoids alternated in field strength and narrowed according to a
pattern
- 137 parameters
- Varied everything individually
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19
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- Decay channel:
- Original design: 3.1% m+ out per p+ from rod
- 12-parameter optimisation à 6.5% m+/p+
- 137 parameters à 9.6% m+/p+
- Re-optimised for chicane transmission:
- Original design got 1.13%
- 12 parameters à 1.93%
- 137 parameters à 2.41%
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20
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21
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- Original design had alternating (FODO) solenoids
- Optimiser independently chose a FOFO lattice
- Has to do with the stability of off-energy particles
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22
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- Nontrivial optimum found
- Preferred length?
- Narrowing can only be due to nonlinear end-fields
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