OPTIMIZED CAPTURE MECHANISM FOR A MUON COLLIDER/ NEUTRINO FACTORY TARGET SYSTEM. HISHAM SAYED 1 X. Ding 2, H. Kirk 1, K.

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1 OPTIMIZED CAPTURE MECHANISM FOR A MUON COLLIDER/ NEUTRINO FACTORY TARGET SYSTEM HISHAM SAYED 1 X. Ding 2, H. Kirk 1, K. McDonald 3 1 BROOKHAVEN NATIONAL LABORATORY 2 University of California LA 3 Princeton University NUFACT 213

2 INTRODUCTION & LAYOUT 2 Muon Capture in Target & Front END Ø Capture Solenoid Field Study: Ø Optimizing quantity: Muon (Pions) count transverse capture - Target Solenoid peak field - Final end field Ø Optimizing quality: Muon (Pions) longitudinal phase space (transverselongitudinal coupling) transverse-longitudinal capture - Taper field profile Ø LOW ENERGY LOW POWER C TARGET Ø Optimizing the time of flight of incident beam (Buncher-Rotator RF phase) Ø Transverse focusing field in decay-channel-buncher-rotator Ø Match to ionization cooling channel for every end field case 1. T à 3. T Ø Performance of front end as a function of proton bunch length Ø Realistic Coil Design & performance optimization

3 MUON COLLIDER/NEUTRINO FACTORY LAYOUT 3 Target System Solenoid: Baseline: Capture µ ± of energies ~ 1-4 MeV from a 4-MW proton beam (E ~ 8 GeV). Low Power: Capture µ ± of energies ~ 1-4 MeV from a 1-MW proton beam (E ~ 3 GeV).

TARGET SYSTEM CURRENT BASELINE DESIGN SC magnets 4 Ø Ø Production of 1 14 µ/s from 1 1 p/s ( 4 MW proton beam) Proton beam readily tilted with respect to magnetic axis.

4 TARGET SYSTEM CURRENT BASELINE DESIGN SC magnets 4 Ø Ø Production of 1 14 µ/s from 1 1 p/s ( 4 MW proton beam) Proton beam readily tilted with respect to magnetic axis. Ø Hg Target Ø Proton Beam Ø E=8 GeV Ø Solenoid Field Ø IDS12h à 2 T peak field at target position (Z=-37.) Ø Aperture at Target R=7. cm - End aperture R = 3 cm Ø Fixed Field Z = 1 m à Bz=1. T Tungsten beads Ø Production: Muons within energy KE cut 4-18 MeV end of decay channel Ø N μ+π+k /N P =.3-.4 Proton beam and Mercury jet Resistive magnets Mercury collection pool With splash mitigator -T copper magnet insert; 1-T Nb3Sn coil + -T NbTi outsert. Desirable to eliminate the copper magnet (or replace by a 2-T HTS insert).

5 LOW ENERGY LOW POWER TARGET SYSTEM SC magnets Ø Ø Ø Ø Graphite target 1-MW proton beam power E=3 GeV Solenoid Field IDS12h 2 T peak field at target position Ø LOWER peak field is being considered ( 2-1T) Tungsten beads Proton beam and Resistive magnets -T copper magnet insert; 1-T Nb3Sn coil + -T NbTi outsert. Desirable to eliminate the copper magnet (or replace by a 2-T HTS insert). cm y z

6 6 TAPERED TARGET SOLENOID OPTIMIZATION Bz(z,R) [T] Initial peak Field B1 Taper length z End Field B2 Inverse-Cubic Taper B z (, zi < z < z f ) = B1' a1 = pb1 B1 [1+ a1 (z z1 ) + a2 (z z1 )2 + a3 (z z1 )3 ] p (B1 / B2 )1/ p 1 2a1 a2 = 3 (z2 z1 )2 z2 z1 (B1 / B2 )1/ p 1 a1 a3 = (z2 z1 ) (z2 z1 ) z [m] Ltaper= [m] Ltaper=1 [m] Ltaper=2 [m] Ltaper=3 [m] 1 1. T z [m] Ltaper= [m] Ltaper=1 [m] Ltaper=2 [m] Ltaper=3 [m] 1 1. T z [m] z [m] z [m] Ltaper= [m] Ltaper=1 [m] Ltaper=2 [m] Ltaper=3 [m] 1 3. T T 2 1 Bz [T] z [m] Ltaper= [m] Ltaper=1 [m] Ltaper=2 [m] Ltaper=3 [m] 1 Bz [T] 1 3. T Bz [T] 2. T 3 Ltaper= [m] Ltaper=1 [m] Ltaper=2 [m] Ltaper=3 [m] Ltaper= [m] Ltaper=1 [m] Ltaper=2 [m] Ltaper=3 [m] 1 Bz [T] 1 Bz [T] 2 Bz [T] R [m] z [m] 2 3 3

7 LONGITUDINAL PHASE SPACE DISTRIBUTIONS (SHORT VERSUS LONG TAPER) 7 End of taper Long adiabatic taper 4 m End of Decay Short taper 4 m

time spread à large longitudinal emittance Short Solenoid taper: Ø Smaller time spread à

8 PHASE SPACE DISTRIBUTIONS (SHORT VERSUS LONG TAPER) 8 Longitudinal phase space at end of decay channel Long Taper 4 m Short Taper 4 m Long Solenoid taper: Ø More particles Ø Large time spread à large longitudinal emittance Short Solenoid taper: Ø Smaller time spread à smaller longitudinal emittance Ø Fits more particles within the acceptance of buncher/rotator

PHASE SPACE - SHORT VERSUS LONG TAPER 9 Pz-T

particles Green: Initial distribution of

Long Taper z= m Ltaper=4. Good Ltaper=4.

9 PHASE SPACE - SHORT VERSUS LONG TAPER 9 Pz-T Correlations at end of decay channel of good particles Green: Initial distribution of good particles which were bunched and cooled in 4D cooling channel Pz [GeV/c] Short Taper Bz=2-1. Long Taper z= m Ltaper=4. Good Ltaper=4. Good.2 Short Taper Long Taper T [nsec] Good Particles

10 DEPENDENCE OF TIME SPREAD & TRANSVERSE EMITTANCE ON TAPER LENGTH 1 Transverse emiiance shaped by capture solenoid Time spread shaped by capture solenoid Difference from Initial Value % Transverse Emittance % Capture Solenoid Taper Length [m] Difference from Initial Value % Increase in Time Spread Capture Solenoid Taper Length [m] Transverse emiiance decreases by 8% with solenoid taper length going 8à 4 m Time Spread increase by 9% with solenoid taper length going 8à 4 m

MARS SIMULATIONS & TRANSMISSION 11 Muon count within energy

muons at m with K.E. 8-14 MeV R ini =7.-1 cm.

38 Muon count at z= increases for longer solenoid taper.37.

11 MARS SIMULATIONS & TRANSMISSION 11 Muon count within energy cut at end of decay channel MARS1 Simulation: Counting muons at m with K.E MeV R ini =7.-1 cm.42 B i =2-1 T r final =3 cm.41.4 N[muons]/N[p] Muon count at z= increases for longer solenoid taper Bz=2 -> 1. T 1 -> 1. T 1 -> 1.66 T 1 -> 1.8 T Zend [m] L taper [cm]

FRONT END PERFORMANCE 12 Muon count within accelerauon acceptance cuts at end of ionizauon cooling channel Before optimizing ionization cooling channel μ+ only After optimizing ionization cooling

12 FRONT END PERFORMANCE 12 Muon count within accelerauon acceptance cuts at end of ionizauon cooling channel Before optimizing ionization cooling channel μ+ only After optimizing ionization cooling channel Muon/proton ~ 3% Bz=2-1.T Bz=1-1.T Bz=1-2.T Taper Length [m] Muon/proton ~ 3% Bz=2-1.T Bz=1-1.T Bz=1-2.T Taper Length [m] Shorter taper provide better quality muons à More muons at end of ionization cooling channel

13 PERFORMANCE DEPENDENCE ON TIME OF FLIGHT (RF PHASE) TOA Protons at z=- 7 cm MARS OLD OLD TOA Protons at z=- 2 cm t=2.44e-9 sec t=2.44e-9 sec t=3.44e-9 sec t=3.44e-9 sec t=4.44e-9 sec t=4.44e-9 sec -BSLINE t=.44e-9 sec t=.44e-9 sec t=6.44e-9 sec t=6.44e-9 sec.1 2 Muon+/proton TOA=.3812e-9 TOA=4.8814e-9 TOA=3.8819e-9 TOA=2.8823e-9 TOA=1.8828e-9 TOA=1.383e-9 TOA=8.8321e-1 TOA=3.8343e-1 TOA= e-1 TOA= e-9 TOA=-2.119e-9 TOA=-3.119e-9 TOA= e-9 Muon Time [nsec] "output.all.dat" u 2 Optimizing RF Phase z [m] Iteration

14 FRONT END PERFORMANCE 14 μ+ only Nmuon/Nproton Bz=2 1.T Bz=2 2.T Bz=2 2.T Bz=1 1.T Bz=1 2.T Bz=1 2.T Taper Length [m] High statistics tracking of Muons through the front end

15 MUON YIELD VERSUS END FIELD 1 Performance of FE as function of Constant solenoid filed in Decay Channel Buncher Rotator (matched to +/- 2.8 T ionization cooling channel) Muon+/proton Proton Bunch length= nsec.16 Bz(Target)=2 T Baseline Constant Bz [T] Muon yield versus end field 2% for every 1 T increase in constant field μ+ only

16 PROTON BUNCH LENGTH 16 Muon yield versus Proton Bunch Length Bz(Target)=1 T Bz(Target)=2 T Muon+/proton Proton Bunch Length [nsec] ~ 3% loss per 1 nsec increase in bunch length

17 LOW ENERGY LOW POWER CARBON TARGET 17 Ø Ø Ø Ø Graphite target 1-MW proton beam power E=3 GeV Solenoid Field IDS12h 2 T peak field at target position Ø LOWER peak field is being considered ( 2-1T) MARS112 simulauons for producuon Muon(Pion)/Proton Distribution at z=. pi+/k+/mu+ pi-/k-/mu- pi+/pi-/k+/k-/mu+/mu Distribution at z=. Pt [GeV/c] Distribution at z= pi+/k+/mu+ pi-/k-/mu- pi+/pi-/k+/k-/mu+/mu-.7.6 pi+/k+/mu+ pi-/k-/mu- pi+/pi-/k+/k-/mu+/mu- Muon(Pion)/Proton Muon(Pion)/Proton Pz [GeV/c] P [GeV/c]

18 18 LOW ENERGY LOW POWER CARBON TARGET Distribution at z=..6 pi 3 GeV mu 3 GeV Muon(Pion)/Proton Pz [GeV/c] Distribution at z=..8 Distribution at z=. 2. All Particles 3 GeV Good Particles.7 Pz [GeV/c] Muon(Pion)/Proton e-9 4e-9 6e-9 Time [sec] 8e-9 1e Time [nsec] 6 7 8

19 OPTIMIZED CAPTURE/FRONT END 19 OPTIMZATION: Ø Solenoid taper profile Bz=2-2. T (Ltaper = m) Ø Solenoid decay channel Ø Time of arrival Ø Broadband match to ionizauon cooling channel Ø Cooling channel B z [T] OpUmum Capture Solenoid Field L taper = [m] L taper =1 [m] L taper =2 [m] L taper =3 [m] μ+ only z [m] Muon/proton Muon/proton % less than 8 GeV protons on Hg baseline Cut 1<Pz<3 MeV/c Z [m]. Cut 1<Pz<3 MeV/c Amp<.3 m Z [m]

NEW SHORT TARGET CAPTURE REALISTIC MAGNET (WEGGEL) 2 Y [m] 2 1.

T Decay channel Triplet On axis field [scale /2 T] Muon Target Capture

Target Magnets 2 1 1 2 2 Z [m] 3 2 Taper Magnets Decay channel Triplet 1

20 NEW SHORT TARGET CAPTURE REALISTIC MAGNET (WEGGEL) 2 Y [m] B z =2 T Taper Magnets B z =1.T Decay channel Triplet On axis field [scale /2 T] Muon Target Capture Magnet Short Taper length =7 m- B=2-1. T Target Magnets Z [m] 3 2 Taper Magnets Decay channel Triplet 1 B z =2 T Muon Target Capture Magnet Short Taper length = m- B=2-2. T Y [m] B z =2.T On axis field [scale /2 T] 1 2 Target Magnets Z [m]

NEW SHORT TARGET CAPTURE MAGNET (WEGGEL) 21 Muon Target Short Taper Magnet taper length =7 m- B=2-1. & 2. T 2 18 16 14 12 1 8 6 4 2 Bz [T].2.2.3 1 Z [m] 1 2 2.

21 NEW SHORT TARGET CAPTURE MAGNET (WEGGEL) 21 Muon Target Short Taper Magnet taper length =7 m- B=2-1. & 2. T Bz [T] Z [m] R [m] Target SC Magnets Field Map calculated from realistic coils Engineering (V. Grave) IDS12_2-1.T7m2+ Cryo 1

Ø Suppress stop bands in the momentum transmission. 1.6 1. 7 m m 1. 1.4 1.4 1.3 1.

22 NEW DECAY CHANNEL REALISTIC MAGNET (WEGGEL) 22 Ø The pions produced in the target decay to muons in a Decay Channel ( m) Ø Three superconducting coils (-m-long ) Bz(r=) ~ 1. or 2. T solenoid field. Ø Suppress stop bands in the momentum transmission m m Axial-field profile of two Decay-Channel modules IDS12L2-1.T 7m Magnet Length [m] Inner R [m] Outer R [m] J [A/mm 2 ]

REALISTIC COIL BASED DECAY CHANNEL SOLENOID STOP BAND STUDY 23 Suppression of stop bands in the Decay Channel: Tracking muons through decay channel 1 cells ( m) optimize magnet design for best

23 REALISTIC COIL BASED DECAY CHANNEL SOLENOID STOP BAND STUDY 23 Suppression of stop bands in the Decay Channel: Tracking muons through decay channel 1 cells ( m) optimize magnet design for best performance Transmission: Constant 1. Solenoid Field %67 IDS12L2to1.T7m %62 Modified IDS12L2to1.T7m %66 N IDS12L2to1.T7m Modified 1. T Channel v2 1. T Channel v2 Optimization Muon P [GeV/c] IDS12L2to1.T7m 1. T constant solenoid field Field generated from Coils Ptot [GeV/c]

24 CONCLUSION & SUMMARY Target Solenoid parameters that affect the particle Capture & Transmission at target or after cooling Initial peak Field Taper length End Field 2- Impact: Short taper preserves the longitudinal phase-space à muons can be captured efficiently in the buncher-phase rotation sections and more muons at the end of cooling. The maximum yield requires taper length of 7- m for all cases (2-1T) (1.-3.T) for any bunch length. 3- Final constant end field increases the yield by 2% for every 1 T increase in the field beyond the 1. T baseline 4- Initial proton bunch length influence the muon/proton yield at the end of the cooling channel ~ 3% reduction per 1 nsec increase in bunch length. - 1-MW proton beam power E=3 GeV à.4 Muon+/proton at end of cooling channel 6- Realistic Coil design for the capture target and decay channel.

The High-Power-Target System of a Muon Collider or Neutrino Factory

The High-Power-Target System of a Muon Collider or Neutrino Factory K. McDonald Princeton U. (August 29, 2014) NuFact 14 U Glasgow KT McDonald NuFact 14 (U Glasgow) August 29, 2014 1 The Target System