1

Nondestructive MeasurementNondestructive Measurementof Charged Particlesof Charged Particles

Kensuke Homma / Kazuhiro HosokawaHiroshima University

１． A novel principle of charged particle sensing２． Verification of the detection principle in a static condition３ . Future prospects

2

Principle of charged particle detectionPrinciple of charged particle detection

Conventional principle developed so farutilizes local inelastic processes such as ionizations and excitations with the typical energy loss above 1eV.

Can we use a quasi elastic process such as macroscopic polarizations with an extremely small energy loss?It opens up a novel charged particle sensing without changing velocities of charged particles.

Is the macroscopic polarization detectable by visible rays? Crystals with the Electro-Optical property combined with the laser readout are suitable for the purpose.

3

Novel principleNovel principle

2204 Rn

eET

R

t

n

Rt

n

cl

e-

Measure instantaneous variation of refractive indexin Electro-Optical crystal by external electric fields.

e-

z

z

xy

y

x

R

x

))5.0(tan(cos 3/11 Ry

TEO Erfn )(

R

e

n

rfln EO

302

)(2

R

Phase retardation

4

How to extract small phase retardation ?How to extract small phase retardation ?

d f

Lens

(x0,y0)

y

zx

(x1,y1) (x2,y2)

Fraunhoffer diffraction at an infinite distance can be obtainedby lens at a short distance.

The diffraction pattern at a focal pointat a focal point corresponds toFourier transformation of input shape of a refractive media.

)},({)(|),(| 00222

22 yxFfyx

5

Diffraction patterns with a thin wire of 50Diffraction patterns with a thin wire of 50mm

Horizontal wire Tilted wire Vertical wire

Pictures taken by wide dynamic range CMOS camera

No wire

Fourier transformation of Gaussian is Gaussian with smaller waist.

Narrowing the wire width makes diffraction pattern extend more outside.

Diffraction pattern keeps vector information on the projection.

Gaussianprofile

6

Verification with LiNbOVerification with LiNbO3 3 in quasi static statein quasi static state

• Electron current: ~1nA• Electron beam diameter: ~50m(FWHM)• Electron kinetic energy: 4keV• Electron beam distance: ~300m• Laser intensity: 1W• Laser wave length: 532nm• Focal length of lens: 10cm• CMOS camera dynamic range: 103dB• CMOS camera exposure time: 20sec• CMOS camera pixel size: 45 x 45 m2 y [m]

Expected # of photons along y-axis

~10-10

E1=E2=0, r13=8.7 pm/V

Sampling here

Index ellipsoid of LiNbO3 crystal

Local phaseretardation

z

xy

E3 e-

7

Experimental setupExperimental setup

Wide dynamic rangeCMOS camera

CW Laser injection

Plastic Scintillater+ PMT for e- monitor

凸 Lens

Flexible opticalfiber bundle

DC e- gun

Coupling toOptical fiber bundle

LiNbO3

crystal

Location of fiber bundle Auto stage+y

+x

8

Shot by shot intensity profiles at focal planeShot by shot intensity profiles at focal plane

BKG(e-off)

BKG(e-off)-BKG(e-off) SIG(e-on)-BKG(e-off)

Focal point

+y

+y

+y+y

9

Future prospect toward Future prospect toward single charged particle detectionsingle charged particle detection

Soviet Physics – Solid StateVol.8, No. 11 (1967) 2758-2760

Ferroelectrics, 2002 Vol.272, pp. 57-62

Large electro-optical coefficient Fast rise and not too long duration timecompared to effective impact time

KH2PO4(KDP)

KD2PO4(DKDP)

KH2PO4(KDP)

T=14.2K

T=4.2K

T=1.3K

LiNbO3

10

Expected diffraction pattern by single electronExpected diffraction pattern by single electron

Developed eclipseflexible fiber bundle

Mask here

11

SummarySummary

• The novel remote sensing technique with laser diffraction readout was qualitatively verified at a static condition.

• In ideal case, even remote sensing of non-relativistic single electron is possible with cooled DKDP crystal and the test experiment is on going.

• If single charged particle is detectable, it would open up many applications like; end-point determination in beta decays with the nondestructive ToF measurement, mass spectroscopy of ionized protein beam and so on.

12

Backup slides

13

x

y

z

= 1mm

=

0.1

mm

Diffraction with square apertureDiffraction with square aperture

Merits at a focal point:1. S/N can be greatly improved compared to conventional interferometry2. Incident photon intensity can be lowered3. Size can be extremely compact4. Pattern is simple compared to grating optics

2222

2

2

2

2

2

2 2,

2)sin()sin(y

fx

fI yx

x

x

x

x

14

One more stepOne more step

x

y

e-

DKDP crystal

Profile of scanning laser

Linear polarizationz

e-

y

z x

Scanning laser

y’ x’

z

zo

zozo

EO

e

z

o

z

o

z

eoo

ErnErnErn

rf

zn

yErn

xErn

xyErzn

yn

xn

633

632

632

22

2632

2632

632

22

22

2

/1

1

/1

1)(

1'1

'1

'1

12111

15

Ultimate goal of this studyUltimate goal of this study

Eend

Cou

nt r

ate

me me

Big issue in particle physicsAbsolute scale of neutrino mass

Big issue in cosmologyAre there relic neutrinos？Lepton number asymmetry btw. and ？

Can we achieve energy resolution beyond 1eV limit by a novel method ？

Eend

Cou

nt r

ate

me<< 1eV

Kinetic energy measurement of beta decay is a key measurement

p

n e-

en

e-

e

p

eepn 3 body decay

epne2 body interaction

2 bodyNeutrino temperature 10-4 eV

Electron kinetic energy

)( enpe

3 body3 body

16

Spectrometer for end-point measurementSpectrometer for end-point measurement

LOI of KATRIN experiment (hep-ex/0109033)

)1(10~10

1

||/||

54

max

min

0

max

min000

eVB

B

E

E

B

BeUEeU

BET

under adiabatic field change

Phase space in the last 1eVjust below E0 is 2x10-13

3H source is ~1013 Bq

Bmax Bmin Bmax

B field-eU0

MAC-E-Filter @ Mainz

17

B1

B2

B3

B4

S1

S2

S3

S4

ToF section MCP plane

Source plane

Detector element

Electrostatic potentialof E0-10eV atanalyzing plane

10-4 eV resolution to 10eV electronwith 10m ToF section may be achievable.

18

R

vt

dr

rd(tan)

r

v

d

Energy loss per single elementEnergy loss strongly depends on R:

If R is small,phonon excitations cause typically meV order energy loss

If R is large,polarization variation may be caused by notaccompanying phonon excitations due to structural phase transition of DKDP crystal. In such a case, energy loss would be expressed as

KR

erEKrdVEloss

0

22

0 4128

7),(

2

1),(

Eloss~0.8x10-7eV for 1, K~103 and R~1m.

19

LiNbOLiNbO33 結晶の電気光学効果を利用した結晶の電気光学効果を利用した非破壊測定の成功例非破壊測定の成功例

hep-ex 0012032

電荷量の依存性 距離の依存性

time (ns)

40MeV/c electrons with 40ps bunch length

20

Time response of KDPTime response of KDP

Ferroelectrics, 2002 Vol.272, pp. 57-62

KDP crystal

21

Shot by shot intensity profiles at focal planeShot by shot intensity profiles at focal plane

BKG(e-off)

BKG(e-off)-BKG(e-off) SIG(e-on)-BKG(e-off)

Focal point

+y

+y

+y+y