re-acceleration of ultra cold muon in j-parc muon facilitynational research foundation grants...

1/30

Re-acceleration of Ultra Cold Muon in J-PARC Muon Facility

Y. Kondo∗, K. Hasegawa, T. Morishita (JAEA) M. Otani, Y. Fukao,

K. Futatsukawa, N. Kawamura, T. Mibe, Y. Miyake, K. Shimomura, T. Yamazaki,

M. Yoshida (KEK) R. Kitamura, S. Li (Univ. of Tokyo) Y. Nakazawa,

H. Iinuma (Ibaraki Univ.) Y. Sue, T. Iijima (Nagoya Univ.) K. Ishida (RIKEN)

N. Hayashizaki (Tokyo Institute of Technology) Y. Iwashita (Kyoto Univ.) Y. Iwata (NIRS)

N. Saito (J-PARC center) S Bae, H. Choi, S. Choi, B Kim, H. S. Ko (SNU)

E. Won (Korea Univ.) G. P. Razuvaev (BINP)

2018/5/4Y. Kondo IPAC18 @Vancouver, BC, Canada

FRXGB1

* [email protected]

2/30

CONTENTS

1. Muon science at J-PARC

2. Muon linac (m linac) for g-2/EDM experiment

3. Demonstration of muon RF acceleration


3/30

1. Muon science at J-PARC

• 2nd generation charged lepton

like electron.

• spin 1

2, direction is easily

measured by decay products →good magnetic probe.

• mm ~ 200 x me

• High penetration

• Sensitive to unknown particles


u c t

bsd

e m t

ne nm nt

quarks

leptons

Courtesy of S. Kondo

e

n

ҧ𝜈𝜏 = 2.2𝜇s

4/30

Transmission muon microscopy

• 3D imaging of living cells using deep

penetration.

• Require extremely small emittance muon

beam ~10 MeV.


5/30

Beyond the Standard Model? – muon g-2


QED Hadronic Weak

0had

Zg = 2

gm …

Beyond SM?

m ?+ + +

SM predictions

BNL E821 ~3s

Ԧ𝜇 = 𝑔𝑞

2𝑚Ԧ𝑆

𝑎𝜇 =𝑔 − 2

2

6/30

THE CHARACTERS


m+

positive muon

m+

e-

neutral Muonium

(Mu: m+e-)

m+

e-

e-

negative Muonium

(Mu-: m+e-e-)

7/30

Conventional muon production process

•Large emittance!


p

p mn

In flight (decay m)

or at rest (surface m)

From accelerator

Production target

8/30

Ultraslowmuons

Ultra Slow Muon (USM) developed at KEK


Generation of thermal muoiumMills, Imazato, Nagamine et al.,

Phys. Rev. Let. 56, 14, p1463 (1986)

Laser excitation fo muoiumChu, Mills, Kuga, Yodh, Miyake, Nagamine et al.,

Phys. Rev. Let. 60, 2, p101 (1988)

USM @ KEKNagamine, Miyake, Shimomura et al.,

Phys. Rev. Let. 74, 24, p4811 (1995)

USM @ RIKEN-RALBakule, Matusuda, Miyake, Nagamine, Shimomura et al.,

NIM B 266, p335 (2008)

USM @ J-PARC

19851987

1990

1999

2010

(2000 K tungsten)

4 MeV

0.2 eV

Re-accelerate

→ Ultra Cold Muon beam

9/30


3GeV proton

Neutron target

400MeV linac

3GeV RCSMLF

Muon target

J-PARC MLFMaterials and Life science Facility

10/30

J-PARC MUSEMUon Science Establishment


U1A

mSR spectrometer

Laser system

for U-line

H-line

Transmission muon

microscope

& g-2/EDM

U1B

Development of

transmission muon

microscope

U-line

USM beamline

Shielding only

11/30


2. Muon linac (m linac) for g-2/EDM experiment3GeV proton

Surface muon

4 MeV

Re-acceleration

212 MeVVery compact

(~66 cm)

storage magnet

Ultra slow muon

25 meV

Silica aerogel

target

12/30

Comparison e, m, p linac

• 200 x me ~ mm (105.7 MeV) ~ mp/9


b = 0.7

40 MeV

13/30

Configuration of m LINAC

• 2-stage frequency, 4-structures.

• Comparable emittance to p linac, but very low intensity.

• p-e linac hybrid.


mS RFQ IH-DTL

0.34MeVb=0.08

4.5MeVb=0.3

40MeVb=0.7

DAW16m3.2m 10m1.4m

5.6keVb =0.01

212MeVb=0.94

g-2 storage magnet

～40m

324 MHz 1296 MHz

DLS

Particle m+

Energy 212 MeV

Intensity 1×106 /s

Rep rate 25 Hz

Pulse width 10 ns

Normalized rms emittance 1.5 p mm mrad

Momentum spread 0.1 %

14/30

Initial acceleration to 5.6 keV


Time structure

en, rms, x =0.38 p mm mrad en, rms, x =0.13 p mm mradPhase space at RFQ entrance

40 mm

Laser

Spot width 6 mm

Pulse length 1 ns

10 mm 10 mm

10 ns

en, rms =

0.38 p mm mrad

en, rms =

0.11 p mm mrad

Electrostatic acc.

And focus

Mu production

target (aerogel)

15/30

324-MHz structure 1. RFQ 0.056 to 0.34 MeV

H- m

Particle mass (MeV/c2) 939.3 105.7

Intervane voltage (kV) 83 9.3

Power dissipation (kW) 330 4.2

Input energy (keV) 50 5.6

Output energy (MeV) 3 0.34


• J-PARC RFQ II (A spare of 30mA RFQ)

16/30

324-MHz structure 2. APF IH-DTL - 0.34 MeV to 4.5 MeV

• TE110 mode (H mode) cavity

• p mode operation 𝑙𝑐 =𝛽𝜆

2

• Alternative Phase Focusing (APF)


Transverse: defocus

longitudinal: focus

focus

defocus

E

H

6-cell prototype cavity

(final version is 16-cell 1.3 m)

𝜙𝑠 < 0 𝜙𝑠 > 0

17/30

1296-MHz structure 1. DAW CCL - 4.5 to 40 MeV

• Section total (15 modules, 16m) 4.5 MW


Cold modelCST model

E0 = 5.6 MV/mDisk and Washer (DAW) structure

18/30

1296-MHz structure 2. Disk loaded travelling wave structure – 40 to 212 MeV


𝐷 =𝛽𝜆

3

2𝜋

3mode

Main parameters of DLS section

Acceleration gradient 20 MV/m

Synchronous phase -10°

Number of acc. tubes 4

D cell length

b synchronous velocity

19/30

Simulated phase-space distribution @ m linac exit


en, rms =

0.33 p mm mrad

en, rms =

0.21 p mm mrad

20/30

E2E simulation summary


Initial RFQ IH DAW DLS

transmission (%) 87 94.7 100 100 100

Decay loss (%) 17 19 1 4 1

en, rms, x (p mm mrad) 0.38 0.30 0.32 0.32 0.33

en, rms, y (p mm mrad) 0.11 0.17 0.20 0.21 0.21

• Good transmission.

• Minimum delay loss and emittance growth.

Emittance evolution from the RFQ

21/30

R. Kitamura (Tokyo, D3)

Y. Kondo

Y. Sue(Nagoya, M1)

Y. Nakazawa(Ibaraki, B4)


3. Demonstration of muon acceleration (2017/10/24~30)

22/30


23/30

50

30

Evolution of the J-PARC RFQ

2018/5/4Y. Kondo IPAC18 @Vancouver, BC, Canada2000 2005 2010 Year

Be

am

cu

rre

nt

(mA

)

x

RFQ I (~2014)

RFQ III (2014~)

RFQ II (to be used as m RFQ)

50mA protoLaser welding

Cu

rre

nt

up

Structure improve

Cu

rre

nt

up

Discharge problem

24/30


RFQs at both ends

25/30

S

• Portable.

• No laser.

• No hard-to-handle target.

• Lower efficiency, larger emittance than USM


Y. Kuang et al., Phys.Rev.A, 39, 6109

e-m+

Surface muonMu-

Al degrader

m+e-e- (x10)

Ultra Slow Muon

Slow (~keV) muon source

26/30

How to identify accelerated Mu- ?


Initial acc

307 ns

GEANT4

RFQ297 cells

2×324 MHz= 458 ns

Diag.

89 keV = b 0.041

L = 0.91m

74 ns

TOF total

839 ns

Penetrated

m+

Accelerated

Mu-

MCP

detector

Surface

muon Al

degrader

5.6 keV 89 keV

27/30

The world’s first RF accelerated muons !


To be published in Phys. Rev. AB

arXiv:1803.07891

28/30

• Considering feasibility

RFQ II + IH proto @ H1 area

• Then toward H-line extension


Step 1

Step 2

29/30

Schedule


2020 ?

• Planned construction period of m

linac is 3 years after budget

approval.

• H1 are will be constructed

as the 1st step.

• Then the building is

expanded.

30/30

SUMMARY

• USM re-acceleration programs are underway at J-PARC muon facility.

• Reference design of m linac for g-2/EDM experiment has been

established.

• Demonstrated the world’s first muon acceleration using RF linac.


This work is supported by JSPS KAKENHI Grant Numbers JP25800164, JP15H03666, JP16H03987, JP15H05742, JP16J07784, the Korean

National Research Foundation grants NRF-2015H1A2A1030275, NRF2015K2A2A4000092, NRF-2017R1A2B3007018, the Russian

Foundation for Basic Research grant RFBR 17-52-50064, the Russian Science Foundation grant RNF 17-12-01036. The muon

acceleration experiment at J-PARC MLF was performed under user programs (Proposal No. 2017A0263).

31/30

THANK YOU FOR YOUR ATTENTION!

Towards the

Muon Linac

re-acceleration of ultra cold muon in j-parc muon facilitynational research foundation grants...

Documents