Muon Cooling

Muon Cooling

Robert D. RyneLawrence Berkeley National Laboratory

Snowmass 2013: Lepton Collider Workshop10-11 April, 2013

MIT

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The future of accelerator-based, energy-frontier HEP in the USA: It’s not that complicated

• We will accept that it is extremely unlikely the US gov't will build a new accelerator facility in the USA for energy-frontier HEP

• We will decide to explore as far into the energy frontier as possible on our biggest existing site in the USA

• We will use the highest accelerating gradients possible• We will collide leptons for maximum energy reach• The facility will be circular to enable multiple passes• We will use the strongest magnets we can build for maximum

energy reach within the facility footprint• We will accelerate heavy particles to limit synchrotron radiation

Someday…

Robert D Ryne, Snowmass 2013 Lepton Collider Workshop (MIT, April 10-11, 2013)

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Someday...

We will collide muons

if it is feasible

Robert D Ryne, Snowmass 2013 Lepton Collider Workshop (MIT, April 10-11, 2013)

Robert D Ryne, Snowmass 2013 Lepton Collider Workshop (MIT, April 10-11, 2013) 4

A staged vision encompassing the Intensity Frontier and the Energy Frontier, but we haven't proven it is feasible yet

2010 ~2020 ~2030

Muon Accelerator R&D Phase

Proton Driver Implementation (Project X @ FNAL)

Intensity Frontier

Energy Frontier

MAP Feasibility Assessment

Advanced Systems R&D

Muon Ionization Cooling Experiment (MICE)

IDS-NF RDR

Proposed Muon Storage Ring Facility (nSTORM)

Evolution to Full Spec n Factory

Collider Conceptual Technical Design

Collider Construction Physics Program

Proj X Ph I

Proj X Ph II

Proj X Ph III & IV

Indicates a date whenan informed decisionshould be possible


Muon cooling is a critical issue for demonstrating feasibility

• Muon beams are "born" with very large emittance

• A high energy collider requires cooling the 6D emittance by a factor of ~1 million

• The muon Cooling subsystem is a critical section of an energy-frontier muon collider


Ionization Cooling


Ionization Cooling

• Energy loss in absorbers• RF cavities compensate for lost longitudinal energy• Cooing w/ 201-805 MHz cavities in multi-Tesla fields


MICE experiment

• MICE aims to initially measure transverse ionization cooling on a particle-by-particle basis


Technology challenges for beamline components of a cooling channel

• Operating vacuum rf cavities in high B field• Operating gas-filled rf cavities in high B field• Developing and operating dielectric-loaded,

gas filled rf cavities in high B field (for HCC)• Developing very high magnetic field solenoids

(for final cooling in an energy frontier collider)


MuCool: R&D program at Fermilab to develop ionization cooling componentsMission:

• Design, prototype and test components for ionization cooling– Absorbers (LH2, solid LiH)– RF cavities– Magnets– Diagnostics

• Carry out associated simulation and theoretical studies• Support system tests (MICE, future cooling expts)• Current focus: RF cavity performance in strong external

magnetic fields


MTA Program Overview

• Goal: Demonstrate a working solution to RF cavity operation in high external magnetic field for muon cooling

• Major MAP deliverable– and near-term technical risk for MICE

• Major impact on cooling channel design and future system tests

• A multipronged approach has been followed a Identify most promising paths for detailed

study


RF in high B-field: Potential Solutions• Better materials: more robust against

breakdown/damage (melting point, energy loss, skin depth, thermal diffusion length, etc.)

• Surface treatment: suppress field emission (SRF techniques, coatings, atomic layer deposition)

• Shielding: iron, bucking coils (IDS-NF option)


RF in high B-field: Potential Solutions

• High-pressure gas: suppress breakdown by moderating electrons

14Robert D Ryne, Snowmass 2013 Lepton Collider Workshop (MIT, April 10-11, 2013)

Magnetic Field Dependence“All-season” Cavity (Muons Inc, LANL)

• Modular pillbox with replaceable endplates

• Designed for both vacuum and high pressure

• Operated in magnet– 25 MV/m at B=0 and 3 T

• Follow-on testing underway. Might be seeing first signs of B-field induced degradation


Future Vacuum Pillbox Cavity R&D805-MHz Modular Cavity (SLAC/LBNL)

• New R&D vehicle for detailed systematic studies– Modular design for easy assembly,

parts replacement– Removable endplates (Cu, Be,

other materials, treated surfaces)– Coupling iris moved to center ring

and field reduced (more realistic design)

– RF design validated by detailed simulation

– Ports for instrumentation– In fabrication @ SLAC– Expected delivery to MTA: Fall `13


805-MHz HPRF Cavity Beam Test• Wide range of parameters

– 1010-3x1011 ppp, 5-50 MV/m– 300-1520 psi H2, B=0 and 3T– Electronegative Dopant Studies:

SF6 and dry air versus concentration– Ion Mobility Studies:

He+air, N2+air, D2• Publication in preparation

– Quantitative theory validated by measurement of energy in H2/D2+dopant

– Electronegative dopants turn mobile ionization electrons into heavy ions, reducing RF losses by large factor

• Results extrapolate well to Neutrino Factory operation and a range of Muon Collider beam parameters– Plasma loading < beam loading– Bunch intensity limits being evaluated

1470psi H2 a w/beam a add 1% dry air


HTS High-Field Solenoid Development

• Plan built on significant results from PBL/BNL YBCO solenoid last year:Bo>15 T (record), Bpeak >16 T with full insert (25 mm, 14

pancakes)Record for magnet fabricated solely with HTS SC

Bo> 6 T, Bpeak > 9 T in half midsert (100 mm, 12 pancakes)• Full midsert worked well (see below) and is ready for test at 4K

The route to a ≥ 30T SolenoidMidsert

Insert


Outlook• Experimental program

– HPRF beam tests successfully concluded• Looks promising for Neutrino Factory and Muon Collider application• Dielectric loading to be tested soon [Fall]

– Vacuum cavity R&D bearing fruit• 25 MV/m @ 3T demonstrated in Cu pillbox (all-season cavity), follow-on testing

underway. Might be seeing first signs of B-field induced degradation. Will be opened for detailed exam late spring.

• Alternative window geometry to be explored [Spring]• New modular cavity in fabrication for detailed systematic studies (Cu/Be walls,

gradient vs B) [Fall]• Beam tests will be included in experimental program• 201-MHz single-cavity module (MICE) tests [Summer]

– Tests with Coupling Coil Magnet will follow when magnet prototype ready

• Infrastructure upgrades (beamline, RF, magnets) • R&D program now pointing the way to RF solutions for

ionization cooling channels!


Beyond overcoming component technology challenges, a full 6D cooling system is still highly complex and challenging

• Forming a bunch train in the Front End via buncher and phase rotator

• Charge separation• 6D cooling

– Guggenheim, Helical Cooling Channel (HCC), FOFO Snake, Rectilinear RFOFO

• Bunch merging• Bunch recombination• Final cooling to reduce

eperp at expense of elong


Helical Cooling Channel (HCC) R&D

• HCC: Dielectric-Loaded RF cavities filled with high pressure hydrogen


Guggenheim R&D• Elements of the Guggenheim:

– vacuum RF cavities– Flip, non-flip, and half-flip lattices

being studied– challenging geometry constraints– High JE required in final stages

• Demonstration magnets on 3 yr timescale for RF tests


Guggenheim lattice


15-stage post-merge Guggenheim tracking results


HPC as an Enabling Capability for MAP

Pre-FY13FY13 onward

Main MAP codes G4Beamline & ICOOL typically run w/ 10K-100K particles using PC’s and clusters

Run times of many hours

“Noisy” simulations due to small # of particles

Not suitable for design optimization

Simplified physics models

G4Beamline & ICOOL parallelized

Ported to 150,000 core supercomputer “Hopper” at NERSC

Simulations now performed with millions of particles

Run times reduced by orders of magnitude

Big impact to MAP D&S effort


Impact of HPC to MAP D&S• Execution time/job reduced from hours to minutes• Muon cooling design w/ parallel G4Beamline code

– Up to 35,000x performance improvement!• Target and front end optimization w/ parallel ICOOL• Studies of space charge in 6D cooling w/ Warp• Parallel design optimization effort underway particles cores time

1 x 106 1 20 hrs

1x 106 480 3 min

200 x 106 9600 ½ hr

Previously, serial jobs were slow and low resolution

Now we can do “small” (~million particle) parallel jobs in minutes

Can do large jobs when needed

Neutrino Factory Front End test problem,Longitudinal emittance vs z. Green: serial ICOOL. Red: Parallel ICOOL.Identical except for stochastics.Differences vanish for large # of particles.


Cooling: Summary and Conclusion• We are making steady progress on:

– Technology R&D• vacuum RF, high pressure RF, high field HTS magnets

– D&S for Cooling system for a collider• Guggenheim, HCC, FOFO-snake, rectilinear RFOFO• 325 MHz a strong possibility (instead of 201)

• Schedule:– Metrics for Cooling baseline selection by end of FY13– Initial baseline selection by ~end of FY14– Paradigm shifts from exploring options to emphasis on strengthening

baseline in FY15-18, feedback to tech-dev, input to 6D demo planning• reduction in exploring alternatives (only mgmt-approved, high-leverage alternatives)

• Much D&S work remains to be done– more realistic modeling (matching, fringe fields,...), collective effects,

start-to-end cooling simulations


• ILC, TLEP, Super-Tristan, CLIC• Muon collider?• A big, new, green-field US

accelerator facility• HEP accelerator facility with its own

accelerator-driven sub-critical system– uses some power for science, sells the

rest and is a money-maker• LPA-based Multi-TeV collider• Muon collider?

Not feasible?A long way off for sure

It's good to have big dreams, but let's not ignore technological feasibility and political realities

Does a muon collider belonghere?

Not in the USA

Politics

Politics + Feasibility(someday just politics?)

Not feasible? Does a muon collider belonghere?

feasibility Muons: the "only game in town" or "no game in town"


The pursuit of muon acceleration, and doing it at a US facility, is not just about building the next HEP accelerator

• It's about laying a foundation for a new type of particle accelerator technology that will affect HEP research for many decades to come

• It's about a US facility that is a magnet for inspiring and training future generations– not the only energy-frontier facility, but one of a few

worldwide• It's about developing new technologies whose

impact beyond HEP is yet to be known– but is likely to be significant if history is a guide

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Muon Cooling