Recent Progress Toward a Muon Recirculating Linear Accelerator

S.A.Bogacz, V.S.Morozov, Y.R.Roblin1, K.B.Beard2, A. Kurup, M. Aslaninejad, C. Bonţoiu, J.K. Pozimski

1Jefferson Lab, Newport News,VA, 2Muons, Inc., Batavia, IL, 3Imperial College of Science and Technology, London, UK

INTERNATIONAL DESIGN STUDY

The International Design Study for the Neutrino Factory (IDS-NF) baseline design

involves a complex chain of accelerators including a single-pass prelinac, two recirculating linacs (RLA) and a fixed field alternating gradient accelerator (FFAG).[1]

Muons, Inc.

ABSTRACT

Both Neutrino Factories (NF) and Muon Colliders (MC) require very rapid acceleration due to the short lifetime of muons. After a capture and bunching section, a linac raises the energy to about 900 MeV, and is followed by one or more Recirculating Linear Accelerators (RLA), possibly followed by a Rapid Cycling Synchnotron (RCS) or Fixed-Field Alternating Gradient (FFAG) ring. A RLA reuses the expensive RF linac section for a number of passes at the price of having to deal with different energies within the same linac. Various techniques including pulsed focusing quadruopoles, beta frequency beating, and multipass arcs have been investigated via simulations to improve the performance and reduce the cost of such RLAs.

3 GeV

1.8 GeV

1.2 GeV

3.6 GeV

244 MeV

900 MeV

2.4 GeV

RLA I

RLA II

Pre-linac244 MeV 900 MeV

3.6 GeV0.9 GeV

3.6 GeV 12.6 GeV

86 m0.6 GeV/pass

202 m

255 m2 GeV/pass

RLA II (arcs not shown)

prelinac

RLA I

* Funding: Supported in part by US DOE STTR Grant DE-FG02-08ER86351. Notice: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.

2020

260

260

Size

_X[c

m]

Size

_Y[c

m]

Ax_bet Ay_bet Ax_disp Ay_disp

24 short cryos 26 medium cryos

(2.5)2eN = 30 mm rad

(2.5)2 sDpsz/mmc = 150 mm

78.91030

150

50

BET

A_X

&Y[

m]

DIS

P_X&

Y[m

]

BETA_X BETA_Y DISP_X DISP_Y

quad gradient

389.3020

300

50

BET

A_X

&Y[

m]

DIS

P_X&

Y[m

]

BETA_X BETA_Y DISP_X DISP_Y

1.2 GeV0.9 GeV 3.0 GeV2.4 GeV1.8 GeV 3.6 GeV

Arc 4Arc 3Arc 2Arc 1

bx = 3.2 m by = 6.0 max =-1.1 ay =1.5 bx,y → bx,y

axy → - axy

bx,y → bx,y

axy → - axy

bx,y → bx,y

axy → - axy

bx,y → bx,y

axy → - axy

bx = 6.3 m by = 7.9 max =-1.2 ay =1.3

bx = 7.9 m by = 8.7 max =-0.8 ay =1.3

bx = 13.0 m by = 14.4 max =-1.2 ay =1.5

1 m

1.75 m

-H V -H-V2 cells

4 cells

-V V

30.50

Bet

a_X&

Y[m

]

DIS

P_X&

Y[m

]

BETA_X BETA_Y DISP_X DISP_Y

H -H V H-H-V2 cells

4 cells

Double achromat Optics

-V V

βx βy Dx Dy

0

20

-1

+1

113.50

200

3-3

BET

A_X

&Y[

m]

DIS

P_X&

Y[m

]

BETA_X BETA_Y DISP_X DISP_Y

Arc 1

1.2 GeV

143.6110

200

3-3

BET

A_X

&Y[

m]

DIS

P_X&

Y[m

]

BETA_X BETA_Y DISP_X DISP_Y

6 m cells

1 m dipoles

Arc 3

2.4 GeV

8 m cells

2 m dipoles

qs = 11.53

qs = 5.72

qin = 12.46

qout = 14.19

qout = 11.53

qin = 13.79

G[kG/cm]=0.3

G[kG/cm]=0.6

B[kG]=9.9

B[kG]=9.9

9 cells in

10 cells in

PRELINACAccelerates μ± from about 244 to 900 MeV total energy and accepts a high emittance beam about 30 cm wide with a 10% energy spread.

PRELINAC TO RLA CHICANEThe current chicane separates the μ± with a dipole, then each is directed down 1.75m into the plane of RLA I, then directed by dipoles into the middle of the linac. On subsequent passes, the injection dipole separates the returning μ±, so a mini-chicane in the linac is used to correct the paths.

FUTURE PLANSThe neutrino factory baseline is being redesigned in light of recent experimental results; it is anticipated that only ~10 GeV is required, so the prelinac and RLAs will need be reoptimized and will feed a decay ring directly.

Beta function beating in the RLA I linac.

Beta functions in RLA I arcs 1 & 3

MULTIPASS ARCSBy combining two arcs into one multipass arc, it is possible to greatly simplify the RLA by eliminating one arc’s chicanes and most of the switchyard.

While pulsed quadrupoles could allow as many as 7 ½ passes, they aren’t needed for 4 ½ passes.

The arc’s cells are constructed of linear combined-functions magnets with variable dipole and quadrupole field components. Unlike a fixed field alternating gradient design, opposing bends are not required.