1. 2. 3. 4. 5. 6.

1.

Cherry 1958 3 10-8, 1968 Groce LINAC - 10-6,

ε ( 1. 7P ρ Dτ em E 1. 14 max eff )

e+ 1. ; 2. 58 Co ; 3.(Au+MgO)

Moderation efficiency (transmission geometry) vs. foil thickness.

Table shows typical values for the efficiency, emission energy and energy spread of selected materials and different geometries.

1986 Gullikson Mills Ne Ar Kr Xe K 22 Na Ne ε 7 10-3 1995 D.Vasumathi Kr 22 Na 4 10-4 2.5±0.1eV

1987 Beling NiSi/Si(111) SiC 1997 Suzuki 5-10kV

With the raw W mesh material having a wire diameter of 20 µm and transmission efficiency of 92.5%, an optimal efficiency of 1.2 10-3 was achieved with 5 min etching duration and a folding number of 12 layers.

Photographs of: (a) the original tungsten mesh and (b) the electro-polished mesh.

France

(1)e+,,, e+. (2), 1)e+,,, e+,. (3), e+, e+.. (4).. (5).

(1) positron beam; (2) solenoid; (3) inner guiding tube (4) accelerator; (5) set of Helmholtz coils; (6) sample;

FWHM=11.6 mm 3 kev,0 3 kev,8 10 kev,16

0-30keV d P( x) = exp[ ( x / x ) 2 ] dx 0

m, r, and A are empirical parameters. ρ is the mass density of the sample and Γ the gamma function. Widely used empirical values are: A = 4.0 µgcm 2 kev r, m = 2, and r = 1.6 (Vehanen et al. 1987). 1nm µm

The positron trapping into defects can occur after thermalization during diffusion.

Fig. 5. Experimental determination of the parameters A and r of the Makhov profile (1).(a) S parameter as a function of the positron energy for amorphous silicon layers ( 1000 nm, 485 nm, 350 nm, 200 nm, 120 nm thickness) grown on 600 nm thick silicon dioxide. The oxide layer was obtained by 1000 C annealing of a Czochralski-grown silicon wafer.

2.

3m x 0.6m x 1.5m Na-22(1.11GBq) 0.5 kev- 20 kev < 250 ps > 300 cps (10 6 counts) 1 40ns - 1000ns / 10-3

10 6 /s 1990, β + 20mCi 22 Na 10 5 /s, 0-25keV 1995 1998

Slow positron beam line including an RI source, the buncher and accelerator.

3.

5 10 6 e + s β + 22 Na β + 1 Ci

1982 Lawrence Livermore National Laboratory Howell 120 MeV 120 MeV 1.2 cm e - -e + e + 9 10 8 /s 1.5 10-6

The LLNL Electron-Positron Beam Facility

!!! " #

$ % &! #! ' (!#! ' ) ' '# ) '! ' '#

$ ' *+, ( - # ( # (. #

1990 Linac 75MeV, 25µm W 2500 C e - 4µA 1 10 7 e + /s 1993 Gent 300Hz 3µm Linac [24], 4 10 7 e + /s 1995 Gakugei 100 MeV, 3 10 7 e + /s 1997 Oak Ridge J.Xu 100nm Mo 15ns 3.9 10 11 e + /s

Linac 1995 Sumitomo Hirose RIKEN Itoh 10 18MeV 27 Al(p,n) 27 Si β + 27 Si 5.8MeV, 27 Si 4.1s, 100%, β + 3.85MeV Hirose Al Al 10µA 1mA, 4 10 7 e + /s 4 10 9 e + /s 1997 30µA 2 10 6 e + /s 1997 T.Kumita 27 Si 5 10 5 e + /s 27 Si 18MeV Al 27 Al(p,n) 27 Si 38%

1993 DESY K.Flottmann 4 10 14 e + /s 10 10-12 e + /s 1996 G.Barbiellini CERN LEP2 85GeV γ 1-2MeV 10 13 e + /s/mev 2-18 MeV 10 13 e + /s/mev 18 MeV

1982 1985 20 90 50 6

4.

Chopping and buncher

Cross-sectional view of the chopper and buncher.

The time structure of the bunched and chopped beam.

Target Chamber Taken to minimize the effect of backscattered positrons.

/ /! ' ( 0 #

$ ( $ 1!

Ghent pulsed positron beam (1) moderation preparation chamber; (2) ) source shielding; (3) prebunch chop system; (4)energy selector; (5) resonator buncher; (6) acceleration section with Faraday cag

A pulsed MeV positron beam line JAERI, Japan

Energy spectrum of an accelerated beam at an input RF power of 110 kw.

For long positron lifetime measurement. Due to the bunching of some slow positrons, many unexpected satellite peaks appear on the tail of the positron lifetime spectrum of a porous thin.

new sine-wave form can effectively work without causing some satellite peaks for the positron lifetime spectrum.

, Ps

5. Polarized positron source 1979 Zitzwitz MgO. 1984 Van House 70%

1997 T.Kumita 27 Si 5 10 5 e + /s 27 Si 4.1s, β + 3.85MeV 18MeV Al 27 Al(p,n) 27 Si Al 2 mm, 18MeV 27 Si β + W 10eV 27m 100G 38%

US-Japan Cooperation in the Field of High Energy Physics Goal of the Cooperative Research Development of polarized positron source for the future linear collider. The linear collider project in Japan, formerly known as JLC (Japan Linear Collider), has received a new name GLC (Global Linear Collider).

GLC is a 30-km, E CM =1TeV electron positron linear collider. Construction starts: 2007 Commissioning: 2013 Spin polarization of both electron and positron beams allows us to make precise observation of exotic processes, such as SUSY particles.

+ + e e W W is a serious background for SUSY particle search. This process can be supressed by factor 11 if. e - : 80% polarization e + : 60% polarization

Basic idea of polarized positron production 20 15 10 5 0 R γ-ray Positron Sum L 0 10 20 30 40 50 60 γ-ray energy [MeV] 800 700 600 500 400 300 200 100 Sum R (Incident photon with right handed) L 0 0 10 20 30 40 50 Positron energy [MeV]

Bunch structure of the e + beam required by GLC

CO 2 laser ( =10.6 m, E=0.117 ev ) e - beam 5.8 GeV -ray E max = 60MeV Thin conversion target e - e + pair creation e - e +

Original design of the pol. e + source utilizing CO 2 lasers Circularly polarized CO 2 laser beams are scattered by a 5.8GeV electron beam. 10 CO 2 laser modules supply laser beams to 200 collision points.

A pair of parabolic mirrors and an axicon expander are placed at each collision point.

A collision section consists of one laser module and 20 CPs.

A 3D schematic drawing of the laser beam path

There are 10 collision sections and 200 collision points in total

Required laser pulse Peak power = 30GW

Development of the short-pulse multi-bunch CO 2 laser is the most difficult part of the polarized positron source. The FEL Option

SUMMARY Short-pulse multi-bunch lasers are required to produce polarized positrons for GLC. We consider use of FELs instead of conventional CO 2 lasers. 1D simulation expects 30GW laser power at saturation of a 10.6µm single-pass FEL with 22m long wiggler. Taking into account the diffraction effect given by 3D dispersion relation of FEL, we expect 14GW laser power at saturation with 40m long wiggler. We need 3D FEL simulations for detailed discussions, especially for tapered wigglers.

1. 2.

1. Detector How to see particles

!" #$ % " "! "

Stopping Power vs. Energy for Protons, Deuterons, and Alpha Particles in Si and Ge.

Average Energy Necessary to Create an Electron-Hole Pair The values of ε are: 3.62 ev in silicon at room temperature; 3.72 ev in silicon at 80 K, and 2.95 ev in germanium at 80 K. Rise Time In most cases T R is the dominant factor. Although a precise calculation of T R can be quite complex, the order of magnitude of T R can be easily obtained by the following formulas: T R W x 10 7 s for silicon detectors at room temperature, and T R W x 10 8 s for germanium detectors at LN 2 temperature.

Hp-Ge detectors

P-Type HPGe Crystal Geometries

N-Type HPGe Crystal Geometries

Three different crystal geometries, all with the same IEEE point source efficiency, but very different absolute efficiency for a puck sample on endcap.

137Cs, 1.33 MeV Point source efficiency curves for planar and coaxial detectors in arbitrary units.

GEM HPGe Coaxial Detector (Non- PopTop or PopTop)

Scintillation counter & " '

photomultiplier tubes convert small light signal (even single photon) into detectable charge (current pulse) photons liberate electrons from photocathode, electrons multiplied in several (6 to 14) stages by ionization and acceleration in high electric field between dynodes, with gain 10 4 to 10 10 photocathode and dynodes made from material with low ionization energy;

photocathodes: thin layer of semiconductor made e.g. from Sb (antimony) plus one or more alkali metals, deposited on glass or quartz; dynodes: alkali or alkaline earth metal oxide deposited on metal, e.g. BeO on Cu (gives high secondary emission);

The amount of light given off by NaI is proportional to the amount energy absorbed. The light yield is ~ 1 photon produced per 100 ev deposited in NaI Photoelectric Effect γ absorbed by material, electron ejected γ Compton Scattering γe - γe - elastic scattering γ Pair Production γ e + e - creates anti-matter γ e - e- e - e + NaI γ hv < 0.05 MeV 0.05 < hv < 10 MeV hv > 10 MeV γ-ray must have E>2m e

How do we get a PEAK in our energy spectrum? A peak in the energy spectrum corresponds to the case when all of the γ-ray s energy is absorbed in the NaI calorimeter. peaks actual energy resolution not all γ energy totally absorbed γ γ γ e - e - e - e + Photoelectric effect and electron stops in NaI. Compton scatter followed by photoelectric effect Pair production e - is absorbed in NaI e + annihilates into 2 γ s γ s undergo photoelectric effect

ORTEC-572A Amplifier PERFORMANCE Gain Range Continuously adjustable from 1 to 1500. Pulse Shape Semi-Gaussian on all ranges with peaking time equal to 2.2τ and pulse width at 0.1% level equal to 2.9 times the peaking time. Spectrum Broadening Typically <16% FWHM for a 60 Co 1.33 MeV gamma line at 85% of full scale for an incoming count rate of 1 to 100,000 counts/s

ORTEC-GG8020 Octal Gate and Delay Generator OUTPUT DELAY Adjustable from <70 to >1000 ns, or from <0.4 to >10. Temperature coefficient <0.04%/ from 0 to 50. OUTPUT PULSE WIDTH Adjustable from <70 to >1000 ns, or from <0.4 to >10ns..DEAD TIME Typically equal to the Delay plus the Output Pulse Width plus 20 ns.

ORTEC-414A Fast Coincidence PULSE PAIR RESOLUTION <100 ns on any single input; for coincidence events, on the coincidence output. RESOLVING TIME (2τ) Continuously variable from 10 to 110 ns for coincidence signals; set by the width of the input pulse for the anticoincidence signal.

ORTEC-426 Linear Gate GAIN Unity. INTEGRAL NONLINEARITY <0.15% from 0.2 to 10 V. PULSE FEEDTHROUGH <10 mv with a 10-V input pulse. TEMPERATURE INSTABILITY <0.015%/ 0 to 50 C.

α α e 2 α = = η c 1 137 α 3 σ σ 3γ 2γ 3 6 α σ 1γ α 4 = = α =, = = α 2 2 α 137 σ α 1 8 2γ 10,

σ σ 3γ 2γ 4 2 = 3 ( π 9) α = 9π 1 372,

2. 2 λ = πr 0 cn e r 0 n e 3 n = d rρ ( r ) ρ ( r ) e v + + τ = 1 λ

Decays of A=22 Nuclei 22 9 F (4.0s) e - + ν 67% e - + ν 33% 3.34 MeV e- electron e+ positron (anti-electron) ν neutrino ν anti-neutrino (2.6 y) n p + e - + ν p n + e + + ν 1.27 MeV 0.00 MeV e + + ν (3ps) 22 11 Na e + + ν γ 0.05% K=2.84 MeV 22 10 Ne

Dominant Decay Chain of 22 Na 1.27 MeV e + + ν (3ps) K=1.57 (2.6 y) 22 11 Na e+ positron (anti-electron) ν neutrino p -----n + e + + ν 0.00 MeV γ Source of 1.27 MeV photons 22 10 Ne

Photon scattering off electron (Compton Scattering) initial General form: final We ll do special case, photon scatters backwards at 180 0 initial final

(

) ( ** ' + γ #,*-. /

Conclusion (1) If a 1.27 MeV photon scatters backwards off an electron,the electrons kinetic energy will be 0.83*1.27 MeV=1.05 MeV Only a small fraction of photons will scatter backwards. Photons scattering at smaller angles will knock out electrons with smaller kinetic energy. Conclusion (2) If 1.27 MeV photons scatter off electrons, the electrons will have a range of kinetic energies. The maximum kinetic energy will be 1.05 MeV. We can measure the kinetic energies of these electrons in a detector.

0 ** ' γ Small sample of 22 Na e γ γ γ NaI Crystal Detector high energy photons collide with electrons in crystal and ionize atoms Electrons reunite in crystal and multiple photons in the visible frequency are released Photomultiple Tube photons from the crystal detector enter vacuum tube and are converted to an electrical pulse

TABLE TOP POSITRONS International List of Positron Annihilation Groups

York University Brandeis University University of California, San Diego Lawrence Livermore National Laboratory University of Louisville University of Michigan Michigan Technological University University of Missouri - Kansas City University of Texas at Arlington Washington State University Wayne State University

University of Vienna University of Geneva Universität Bonn Martin-Luther-Universit, Halle TU München ELBE Positron Source, FZ Rossendorf MPI Stuttgart Helsinki University of Technology University College, London Royal Holloway College, London University of Wales at Swansea

Institute of High Energy Physics, Beijing University of Science and Technology of China Wuhan University Hong Kong University KEK Radiation Safety Control Centre KEK Slow Positron Facility Kyoto University Osaka University Tohoku University Tokyo Metropolitan University Tsukuba Electrotechnical Laboratory