lsw experiments with pulsed magnets +vacuum …...k

LSW experiments with pulsed magnets+Vacuum Magnetic Birefringence (VMB)

HIMAFUN 30th May 2017

Toshiaki Inada

•  Magnet/bank: T.Yamazaki et al, NIM A 833, 122 (2016)

•  VMB: X.Fan et al, arXiv: 1705.00495

•  X-‐ray LSW: T.I. et al, PRL. 118, 071803 (2017)

1

Fundamental physics in vacuum

Be Be

a

Be Be

a

Be

a

Be

Light-‐by-‐light interac0on VMB

VMB

LSW

Nonlinear QED Axions, ALPs

We are studying both of these nonlinear QED and axions 2

Haloscope, Helioscope

Pump-‐probe scheme for vacuum physics

Laser (~1 PW) Pulsed magnet

Laser (op^cs)

X rays (XFEL)

Laser LSW VMB

X-‐ray LSW Laser-‐induced diffrac^on/birefringence

Light-‐by-‐light sca`ering Four-‐wave mixing

We use pulsed pump to get a high field

Probe Pump

3


Probe Pump Laser

(~1 PW) Pulsed magnet

X rays (XFEL)

Laser LSW VMB


X-‐ray LSW

4

XFEL PW laser

Diffracted x rays (with flipped pol.)

A 0.5-‐PW laser will be available from 2018 à Now tes^ng with 2.5 TW (link: h`p://tabletop.icepp.s.u-‐tokyo.ac.jp/Tabletop_experiments/VB__SACLA+laser_files/seino-‐lnpc17.pdf)

Laser (op^cs)

Laser-‐induced diffrac^on/birefringence

Pulsed magnets Magnet types •  Solenoid: good symmetry à 80-‐100 T -‐  We need a transverse field over large length •  Racetrack: bad symmetry à 31.7 T (XXL-‐coil) Merits -‐  Intensity: LSW: B×L, VMB: B2×L -‐  VMB with IZ scheme: temporal field modula^on Drawback Low duty: fast repe^^on -‐  Power supply: charging ^me of capacitors, 0.1 Hz -‐  Magnet: hea^ng <-‐> cooling efficiency (LN2) à as high as possible, hopefully to 0.1 Hz

5

Light Magne^c field

Current

Coil structures

Bobin

Lem pole Right pole (rewound)

Dipole

Single coil

Minimalized field-‐volume

Crack at 9 T

6 No a`rac^ve force with a single coil

20 cm

20%

Field map along the beam path •  Transverse field along the pipe center (inner diameter 5.3 mm） •  Tilted path (2.75°) à smaller for the edges

20 cm

Beam pipe Bobin

Dot: measurement Line：finite element simula^on in 3D (ANSYS)

7

Conven^onal backup metal

Coil

(Lem) fipng the coil into a backup ring, (right) pressing it with plates Drawbacks •  Expansion force (Maxwell stress) concentrates on the ring corners •  Large eddy current runs in the ring and plates to cancel the field

Expansion

Eddy current1 (ring)

Eddy current2 (top/bo`om plates)

8

Position (mm)-150 -100 -50 0 50 100 150

B/I (

T/kA

)

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

Dividing the metal into 20 pieces 積層補強を被せる前の，裸のコイル（5号機）

•  Avoid the concentra^on of the expansion force •  Divide the backup metal where eddy current runs

Reducing materials with small thermal conduc^vity à Cooling efficiency

Number of divisions ― 3 ― 7

― 20 ― 40

9

time [ms]0.5 1 1.5 2 2.5

I [kA

]

0

2

4

6

8

10

time [ms]0 1 2 3 4 5

I [kA

]-6-4-202468

10

Power supply for high-‐rep. opera^on •  Lem: conven^onal single-‐shot circuit •  Right: energy recycling circuit

One cycle •  Frist pulse (SCR1) à posi^ve field •  Second pulse (SCR2) à nega^ve field •  Re-‐charge the capacitor by the energy lost by the two pulses

First

Second

10

12 capacitors in total: 3mF, 1.9t à Dividing them into 4 units for transportability Max. voltage: 4.5kV (30 kJ)

2m

1.7m

①

② ③

④ Capacitor units

Discharge sec^on Control panel

11

# of shots0 2 4 6 8 10 12 14 16

[T]

peak

, cen

ter

B

8.6

8.8

9

9.2

9.4

9.6 / ndf 2 2.047e-05 / 11

p0 0.0005752± 8.722 p1 0.5002± 0.6619 p2 1.775± -0.8172 p3 0.03466± 2.334

/ ndf 2 2.047e-05 / 11p0 0.0005752± 8.722 p1 0.5002± 0.6619 p2 1.775± -0.8172 p3 0.03466± 2.334

Con^nuous operaôn Operaônal condiôn •  4 magnets à 0.8 m •  4 kV -‐ 3 kV: 9.2 T – 6.0 T cycle •  cycle repe^ôn: 0.1 Hz •  Heat loss: 2.4 kW for 4 magnets

Pulse interval is adjustable: 30 Hz in this case Fields are stable(± 0.5%) amer reaching equilibrium

Decay of peak field of the first pulse

12

732 pulses

Summary: current status of the field-‐generaôn system

Development of a field-‐generaôn system suited for repe^^ve operaôn -‐  Mul^ple racetracks à small field-‐volume, small hea^ng, high cooling efficiency -‐  Power supply for a high-‐rep. use à energy recycling scheme 9 T over 0.8 m with 0.1 Hz (cycle) has been achieved à B2×L = 54 T2 m -‐  NIM A 833, 122 (2016)

13


Probe Pump Laser


Laser

X rays (XFEL)

Laser LSW VMB



PD Laser

14

The OVAL experiment Observing VAcuum with Laser -‐  Tes^ng setup with one magnet -‐  B2×L = 13.8 T2 m

Electrode

Magnet

2.4 m

Vacuum chamber

Mirror

Polarizer

15

Con^nuous DAQ large gamma: two possibili^es 1.  laser not hipng

the center of the mirrors

16

shields for leakage fields

Side view

To observe VMB, a long-‐term run is necessary -‐  Cavity resonance has to survive pulsed fields We must remove the disturbance of mechanical shocks -‐  The disturbance is decoupled by these bellows?

At present, it works

It

Typical response of PDt

During the pulse -‐  No mechanical shock was observed at 9 T

ARer the pulse Acous^c shock: arrives at 4 ms à Resonance survives

17

N2 measurement

18

Pressure (Pa)0 50 100 150 200 250 300 350 400

)-2

) (T

2(N

CM

k

14

12

10

8

6

4

2

01510×

/ndf 2.825 / 22

8.6e-16±) 1.3e-15 -2 (TCM, vack 4.1e-18±) -3.7e-17 -1Pa-2)(T

2(NCM

Pressure (Pa)0 50 100 150 200 250 300 350 400

)-1) (

T2

(N Fk

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1210×

/ndf 3.855 / 22

7.3e-14±) -8.3e-14 -1 (TF, vack 3.8e-16±) 4.5e-15 -1Pa-1)(T

2(NF

We also measured kCM and kF of N2 gas (100-‐350 Pa)

Preliminary

Vacuum measurement

Fi`ed for 100 cycles

Preliminary kCM = -0.5±1.1×10-18 (T-2)

As a test, we applied 100 cycles of 9.0 T and -‐4.5 T à 15 min

19

Future steps

This measurement Target value Gain Upgrade plan/Status

Magne7c filed 9[T] 15[T] 2 Changing wound wire from Cu to Ag-‐Cu

Field length 0.2[m] 0.8[m] 4 Preparing for loading 4m op7cal bench now

Pulse width 1.2[ms] 4.8[ms] 2 The Modifica7on of the power supply unit.

DAQ 7me 15[min] 180[days] 130 Building a stable DAQ system is on going

Finesse 350,000 650,000 2 Upgrade is succeeded

Intensity 0.03[mW] 5[mW] 40 Upgrade is succeeded

Intensity noise

1×10-‐4 [1/√Hz]

1×10-‐5 [1/√Hz]

3 Upgrade is succeeded

Improvements of op^cs have almost finished We need to combine it with magnets -‐  Work in progress!

Table of improvements to observe QED with a 6-‐month run

20


Probe Pump Laser


Laser

X rays (XFEL)

Laser LSW VMB



21 Pioneering work at ESRF: PRL 105:250405 (2010 )

X-‐ray LSW search for ALPs •  First-‐phase experiment: -‐  DC x rays at SPring-‐8 BL19LXU: 3×1013 photon/s at 9.5 keV -‐  using 4 magnets -‐  2 days for DAQ in Nov. 2015 à 27,676 pulses!

12 vessels (LN2 100 l)

XFEL SACLA

SPring-‐8

22

Opt. hutch Exp. hutch 1 Exp. hutch 2

XPD1

S2 LSW setup

BL19LXU undulator

DCM TRM Slit

W1 W2

W3 RL LPD S1

Ge crystal

3 m

Setup

23

Time-‐energy distribu^on of events

Tim

e (s

)2

4

6

8

Energy (keV)2 4 6 8 10 12 14 16

Tim

e (m

s)

05

10

Signal region

0Time (ms)0 1 2

(T)

0B

-5

0

5

10

First pulse

Second pulse

•  Time window: 2.1 ms (lem) •  Energy window: beam energy (9.5 keV) ±2σ(detector resolu^on)

Signal region

No events!

Energy threshold Beam energy

Monotonic environmental BG

Zoom around the ^me window

24

Limits on the coupling constant

(eV)am-210 -110 1

)-1

(GeV

ag

-410

-310

-210

ESRF (2010)

SPring-8 (2017)

SACLA, 4 magnets (expected)

SACLA, 8 magnets (expected)

•  Next target: XFEL + 8 magnets -‐  4×1011 photon/pulse, 30 pulse/s, 2-‐day run •  Also, keep improving the magnet

5.2 PRL. 118, 071803 (2017)

25

Test of 8 magnets at SPring-‐8

Upstream 4 magnets

Downstream 4 magnets in LN2

Capacitor bank

26

Summary

We develop racetrack pulsed magnets and study vacuum physics (nonlinear QED, ALPs) with combina^on of x rays and op^cal lasers. We keep improving our magnet toward higher fields. Using the present version of magnets and XFEL, -‐  VMB -‐  x-‐ray LSW -‐  vacuum diffrac^on/birefringence experiments have started and begun to obtain results in their first phase.

27

lsw experiments with pulsed magnets +vacuum …...k

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