Nondestructive Measurement of Charged Particles

1. Nondestructive Measurementof Charged Particles Kensuke Homma / Kazuhiro Hosokawa Hiroshima University １．A novel principle of charged particle sensing ２．Verification of the detection principle in a static condition ３. Future prospects

2. Principle of charged particle detection • Conventional principle developed so far • utilizes 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 principle Measure instantaneous variation of refractive index in Electro-Optical crystal by external electric fields. y y x x z z R e- e- Phase retardation

4. How to extract small phase retardation ? Fraunhoffer diffraction at an infinite distance can be obtained by lens at a short distance. y Lens y(x1,y1) y(x2,y2) y(x0,y0) z x d f The diffraction pattern at a focal point corresponds to Fourier transformation of input shape of a refractive media.

5. Diffraction patterns with a thin wire of 50mmf Pictures taken by wide dynamic range CMOS camera Gaussian profile Tilted wire Vertical wire No wire Horizontal 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.

6. Index ellipsoid of LiNbO3 crystal Verification with LiNbO3 in quasi static state y x z E3 e- • Electron current: ~1nA • Electron beam diameter: ~50mm(FWHM) • Electron kinetic energy: 4keV • Electron beam distance: ~300mm • Laser intensity: 1W • Laser wave length: 532nm • Focal length of lens: 10cm • CMOS camera dynamic range: 103dB • CMOS camera exposure time: 20msec • CMOS camera pixel size: 45 x 45 mm2 E1=E2=0, r13=8.7 pm/V Expected # of photons along y-axis Local phase retardation dG~10-10 Sampling here y [mm]

7. Experimental setup Coupling to Optical fiber bundle Wide dynamic range CMOS camera LiNbO3 crystal CW Laser injection DC e- gun Auto stage 凸Lens Location of fiber bundle +y Plastic Scintillater + PMT for e- monitor Flexible optical fiber bundle +x

8. +y +y +y Shot by shot intensity profiles at focal plane BKG(e-off) Focal point SIG(e-on)-BKG(e-off) BKG(e-off)-BKG(e-off) +y

9. Future prospect toward single charged particle detection Fast rise and not too long duration time compared to effective impact time Large electro-optical coefficient KH2PO4(KDP) KD2PO4(DKDP) DT=14.2K DT=4.2K LiNbO3 KH2PO4(KDP) DT=1.3K Soviet Physics – Solid State Vol.8, No. 11 (1967) 2758-2760 Ferroelectrics, 2002 Vol.272, pp. 57-62

10. Expected diffraction pattern by single electron Developed eclipse flexible fiber bundle Mask here

11. Summary • 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. Diffraction with square aperture y z x n = 0.1mm m = 1mm • Merits at a focal point: • S/N can be greatly improved compared to conventional interferometry • Incident photon intensity can be lowered • 3. Size can be extremely compact • 4. Pattern is simple compared to grating optics

14. y’ x’ z One more step y y DKDP crystal z x x z Linear polarization e- e- Scanning laser Profile of scanning laser

15. 3 body decay e- p ne n n e- ne p Ultimate goal of this study Big issue in cosmology Are there relic neutrinos？ Lepton number asymmetry btw. n and n？ Big issue in particle physics Absolute scale of neutrino mass Kinetic energy measurement of beta decay is a key measurement 2 body interaction Count rate Count rate Neutrino temperature 10-4 eV 2 body 3 body 3 body mne<< 1eV mne mne Eend Eend Electron kinetic energy Can we achieve energy resolution beyond 1eV limit by a novel method ？

16. Spectrometer for end-point measurement MAC-E-Filter @ Mainz B field under adiabatic field change -eU0 Bmin Bmax Bmax LOI of KATRIN experiment (hep-ex/0109033) Phase space in the last 1eV just below E0 is 2x10-13 3H source is ~1013 Bq

17. Electrostatic potential of E0-10eV at analyzing plane B2 ToF section MCP plane B4 Source plane B3 B1 S3 S1 S4 Detector element 10-4 eV resolution to 10eV electron with 10m ToF section may be achievable. S2

18. vDt rd(tanq) dr r R dq q v Energy loss per single element Energy 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 not accompanying phonon excitations due to structural phase transition of DKDP crystal. In such a case, energy loss would be expressed as Eloss~0.8x10-7eV for g~1, K~103 and R~1mm.

19. LiNbO3結晶の電気光学効果を利用した非破壊測定の成功例LiNbO3結晶の電気光学効果を利用した非破壊測定の成功例 hep-ex 0012032 40MeV/c electrons with 40ps bunch length 電荷量の依存性 距離の依存性 time (ns)

20. Time response of KDP Ferroelectrics, 2002 Vol.272, pp. 57-62 KDP crystal

21. +y +y +y Shot by shot intensity profiles at focal plane BKG(e-off) Focal point SIG(e-on)-BKG(e-off) BKG(e-off)-BKG(e-off) +y