Development of the Pulsed Magnetic Kicker for the Spiral Injection Test Experiment
Muhammad Abdul Rehman1, Hiromi Iinuma3, Satoshi Ohsawa1,2, Hisayoshi Nakayama1,2, Kazuro Furukawa1,2
Tsutomu Mibe1,2, Hiromi Hisamatsu2
1The Graduate University for Advanced Studies(SOKENDAI)
2 High Energy Accelerator Research Organization(KEK)

rehman@post.kek.jp

3Institute of Quantum Beam Science of Graduate School of Science and Engineering, Ibaraki University

Abstract

A new muon g – 2 / EDM experiment at J-PARC (E34) is under preparation in order to resolve a 3 sigma discrepancy of muon anomalous magnetic dipole moment between the measurement and thestandard model prediction. The E34 experiment will employ a unique three-dimensional spiral injection scheme to store the muon beam into a small storage orbit. In order to demonstrate thefeasibility of novel injection scheme, the Spiral Injection Test Experiment (SITE) with the electron beam is under construction at KEK Tsukuba campus. In SITE, 80 keV DC electron beam was injected atforty degree into the storage magnet and detected as a fluorescent light due to the de-excitation of the nitrogen gas. The pulsed electron beam and a pulsed magnetic kicker are developed in order tokeep the pulsed beam to the very center of the storage magnet. The magnetic kicker produced the radial field to reduce the pitch angle of the injected beam to keep the beam at the storage region. In
this poster, the development of magnetic kicker, tracking studies in kicker field and designs for the SITE’s kicker are presented.

1. Introduction
The muon's anomalous magnetic moment is one of biggest discrepancies inelementary particle physics and extremely sensitive to the new physics. The
most recent measurement of muon g - 2 results in 3 σ discrepancy between
measured and standard model prediction. The J-PARC new muon g – 2 / EDM(E34) experiment is aiming to measure muon g – 2 to the precision of 0.1 ppm
and EDM down to the sensitivity of 10-21 e.cm.

Hadronic

1. Inject beam atvertical angle
in solenoidal
Storage magnet

The three-dimensional spiral injection scheme isan unproven idea, therefore, a demonstration
experiment to prove the feasibility of this uniquescheme is inevitable. A scale down Spiral Injection
Test Experiment (SITE) by the use of electron beam
is under development at KEK Tsukuba campus.

+-𝝁_2.Pulsed Magnetic Kicker

Radial fringe field ofthe storage magnetdecrease injection
to some value
remaining angle isdecreased bymagnetic kicker

Coupled Beam

The pulsed magnetic kicker have to produce the radial the required magnetic field and stopping volume
may calculate as follow

Where 𝜽𝒑𝒊𝒕𝒄𝒉 (=𝒎𝒆𝜽𝝎
𝟐 𝒒 𝒑𝒊𝒕𝒄𝒉

𝒁𝟎 =𝒄 𝑻𝑷𝜸𝒆 𝒎𝒆 𝟒 𝒛𝟎

𝑷𝒛𝟎𝟐𝝅) is the pitch angle of the beam, 𝝎(= ) is the angular frequency.
𝑷𝑻3. Tracking in Kicker Field

Injection region

Tracking with different
Injection angles

OutsideofStorage
Magnet

E3440

SITE
80~100Gauss25300

0.296

7.4

5.03 [T]TypeKicker
ShapeT(ns)

Bkick
(G)

1𝟐𝝅

95

0.079

Pitchangle
ψ (rad)
0.018

2𝝅/𝟒

95

0.638

0.018

3𝝅/𝟔

95

0.948

0.018

4𝝅/𝟏𝟎

95

1.58

0.018

Kicker Design

Storage& kicker region

Outside of Storage Magnet

Injection region

Outside ofStorage
MagnetStorage& kicker region

𝒁𝒓𝒓 𝝏𝑩n=− 𝟎 𝒛𝑩𝟎 𝝏𝒓

Parameters
Storage Magnetfield
Injection Angle(Degree)Momentum[MeV/c]Cyclotron period[nsec]In the case of 2π (uniform) kicker with long time period the requirement for the magnetic
field reduce drastically. One way to overcome the issue of low magnetic field is to reduce
the kick region of the magnetic kicker. The higher magnetic field will be required to kick thebeam due to the limited area of the kicker field. Therefore, we considered kicking the beamwith π/4, π/6 and π/10 shapes instead of the uniform 2π kick.

SITE Storage Magnet Field Profile

𝑩𝒓 = −𝒏 𝑩𝟎¾Smooth connection between injection
and storage section¾All in one storage magnet, which reduce
source of error fields¾No need to kick within a single turn.

4. Alternative Kicker Configurations

The tracking studies has been carried out in order to find the motion of the particle in the kicker field.
Below plots are the shows that how the particle pitch angle decrease in the kicker and particles withresidual pitch angle get trapped in the weak focusing field. Even after the kick, there will be residual
pitch angle, in order to compensate the effect of the residual pitch angle the weak focusing has been
introduced in the storage volume. In the weak focusing field the beam motion will be oscillatory in thestorage volume. The weak focusing magnetic field can be defined as follow∆𝒓
𝒁𝟐
𝑩𝒁 = 𝑩𝟎 𝟏 − 𝒏 + 𝒏 𝟐𝒓
𝟐𝒓

¾Salient Features

The electron beam was detected as a fluorescent
due to the de-excitation of nitrogen gas.

A pulsed magnetic kicker is used to decrease
the pitch
angleKEK-LINAC(ψ) of the beam.
Below figure
SITE setup
at thebuilding
is illustrating the character of the magnetic kicker. The black trajectory is showing themotion of the beam inside the storage magnet without kicker, the beam crosses themiddle region of the storage magnet without stopping. Pink trajectory represents thesituation when an appropriate kick is applied to the beam, which stops the beam in themiddle region of the storage magnet.

𝑩𝒓 =4. Beam will store at the mid plane under theweak focusing field

Bx

BSM

Weak

Electric Dipole Moment
Time reversal

Three-dimensional
New Spiral Injection
Scheme Injection
3. Vertical Kicker will reduce thereaming pitch angle to zeroNot applicable for small
storage orbit due technicalchallenges
QED

𝝁Conventional Injection Scheme

2. Radial Fringe
field reduce
Injection angle𝒈−𝟐
𝒂𝝁 =𝟐+

1.1 Three-dimensional Spiral Injection Scheme

The kicker shape design and magnetic field calculation has been carried out in CST.
2π kicker, two pairs of circular coils

π/6, Rectangular coils (dipole) will work

Storage& kicker
regionStorage& kicker region

Injection region

Bkick(G)ψ0 (rad)1

Injection
PitchTangle
angle
(ns)
(Radian) Ψ(Radian)at Z = -100mm
0.81
0.19
152.410.005

20.71

0.08

31

0.6-0.003

30.67

0.05

48

0.27

-0.004

4

0.66

0.035

62

0.16

10-2

50.64

0.018

95

0.07

10-3

TypeStorage
Under weak focusing

Future Plan and Conclusion
A pulsed magnetic kicker is being under development for the SITE to guide the electron
beam at the center of the storage magnet. Particle tracking studies have been carried out
with the different initial conditions in the kicker and weak focusing field in order to findthe required magnetic field and time period for a kicker. From tracking studies it has beenfound out that the localized kicker will fulfil the requirement for the SITE. We willcomplete the construction of the pulsed kicker power supply and test our pulsed magnetic
kicker with the electron beam within Japanese FY2018.