Channeling Experiments with Electrons at the Mainz Microtron MAMI

Transcription

1 Channeling Experiments with Electrons at the Mainz Microtron MAMI 1. Motivation 2. Channeling Experiments with Frascati 3. Channeling Experiments with Mainz 4. Measurements of the Dechanneling Length 5. A Planar Channeling Experiment with Electrons using a Periodic Graded Composition Strained Layer SiGe Target 6. Conclusions Channeling 2008, Erice, Italy, Oct W. Lauth, University of Mainz, Germany

2 Undulator Radiation at Positron/Electron Channeling in a Single Crystal A. Solov yov, A. Korol, W. Greiner et al.

3 Positron Channeling in Si-Undulator Crystal U x e MeV 2 x A cos z A = 9 Ǻ, U = 50 µm, N U = 4 U Beam Energy E = 600 MeV, = K A c Photon energy k (1 K / 2 ( )) U x y at 0, and first order k 1 x y U 67.9 kev z

4 Channeling Experiments with Frascati

5 Beam Test Facility (BTF) (See Poster Lina Quintieri) Emittance: x = y = 10 mm mrad Divergence: ' x = ' y = 2 mrad ( 0.27 mrad) C Experimental Hall Beam Spot Size: x = y = 5 mm (rms) Energy: MeV Particles: per pulse Repetition rate: 50 Hz Slit for Energy Definition 800MeV Electrons, Positrons from Linac Conversion Target

6 Experimental BTF 250 mm Plastic Scintillator Pb beam dump 350 mm 2" NaI Detector Pb shield d = 2600 mm Goniometer with Si- Crystal Mylar Window d =0.04 mm Be Window d = 0.5 mm e +

7 NaI Signal [a.u.] (normalized over beam intensity) Experimental Result [mrad]

8 Improvement of the Beam line Detectors To Beam Dump Additional 45 Magnet BTF Hall Target Chamber Existing 45 Magnet

9 Experiments with Electrons Dechanneling Length

10 The Mainz Microtron MAMI Parameter: Energy: 180 MeV 1507 MeV Emittance x =9 nm rad, y =0.5 nm rad Energy Stability: µA cw e - - beam X-ray Research Phase Contrast (Beamspot ~1µm) X-ray Interferometry (Magnetic circular Dichroism) PXR, TR, Channeling W. Lauth et al., Coherent X-Rays at MAMI, Eur. Phys. J. A 28, (2006) 185.

11 Experimental Setup (855 MeV e - ) ZnS Screen Camera Beam Dump Top View Ionization Chamber - e Si Target BM m NaI Detector (10" 10" length) Rad. Length X 0 =10 Pb 100 mm 20mm

12 Target Setup and Definition of Angles Top View y y Polar Angle Tilt Angle - e x Azimuth x - e

13 Video of the Beam Spot at the Dump Screen

14 Dumpphotos

15 Evernts [1/s] Evernts [1/s] NaI Raw Spectra 174µm Si Crystal 0,3 0,2 0,1 (100) 1 (111) (110) <111> <100> <110> off Channeling 0,0 0,3 (110) 0,1 (100) 0,2 0,1 0,01 Off Channeling [kev] 0,0 0,3 0,2 0,1 (111) 0, [MeV]

16 Events Energy angle dependence of the radiation (011) (013) (001) (011) (010) 20 E [MeV] 10 6 MeV 0.6 MeV Angle [mrad] Channeling and Quasichanneling

17 Events Energy angle dependence of the radiation E [MeV] 100 Coherent Bremsstrahlung 50 Pulser Angle [mrad] High energy Bremsstrahlung

18 Events Dechanneling E e =855 MeV Photon energy: > 100 MeV (Bremsstrahlung) f x f e xd / ( ) 0(1 ) d (19.6 1) µm Crystal Thickness [µm]

19 Events [1/pA] Dechanneling E e =195 MeV Photon energy: > 12 MeV (Bremsstrahlung) f x f e xd / ( ) 0(1 ) d (18.5 3) µm Crystal Thickness [µm]

20 U [a.u.] Dechanneling E e =855 MeV Photon energy: < 5 MeV (Channeling Radiation) 0,30 0,25 0,20 0,15 0,10 0,05 No saturation Can be explained with channeling / rechanneling processes Fokker-Planck Equation -> d 18µm 0, Thickness x [µm] H. Backe et al. NIM B 266(2008) 3835

21 Dechanneling Length [µm] Dechanneling Length versus Electron Energy µm/gev Electron Beam Energy [MeV]

22 Channeling with periodically bent crystals

23 Experimental Ionization Chamber Goniometer Beam Dump Top View Tagger Magnet NaI Detector (10" 10" length) - e Si-Crystals Undulating crystal Flat crystal 2.7 m Aperture 3mm m Pb 100 mm 45mm

24 Signal Ionisation Chamber (log) [V] no Channeling (111) (100) Scan around the vertical axis Φ Bent crystal -1,5-2,0-2,5 Aarhus-Kristall wipp=-1.8 Psi=178 Phi:-10 -> /s (110) -3,0-3,5-4,0-4, [Degree]

25 Signal Ionisation Chamber (log) [V] no Channeling (100) (111) Scan around the vertical axis Φ Flat crystal -1,0-1,5-2,0 Flat Crystal 200 µm wipp=-1.8 Psi=178 Phi:-10 -> /s (110) -2,5-3,0-3,5-4, [Degree]

26 Events [1/s] Direktory: C:x1messpc2\StrahlzeitdatenX-Strahlzeiten\CU-beiA uswertung\, File: Online new.opj Worksheet: Dat1_B, Grafikfenster: RohspektrenP Rohspektren ohne Skalierung nur Zeitnormiert Raw Data Aarhus 110 Aaarhus No-Channeling 200mu mu No-Channeling 1 0, Energy [kev]

27 Events [1/s] Direktory: C:x1messpc2\StrahlzeitdatenX-Strahlzeiten\CU-beiA uswertung\, File: Online new.opj Worksheet: Dat1_B, Grafikfenster: Graph3 Rohspektren ohne Skalierung nur Zeitnormiert Raw Data Aarhus 110 Aaarhus No-Channeling 200mu mu No-Channeling Energy [kev]

28 Events [1/s] Direktory: C:x1messpc2\StrahlzeitdatenX-Strahlzeiten\CU-beiA uswertung\, File: Online new.opj Worksheet: Dat2_B, Grafikfenster: Channelingstrahlung Differenzen Peak - Aulßerhalb ohne Skalierung Channeling Spectra (110) Plane 4 Diff-Aa-110-U Diff-200mu-110-U Energy [kev]

29 Direktory:, File:.opj Worksheet: dat3_c, Grafikfenster: Graph1 Events Events Direktory: C:x1messpc2\StrahlzeitdatenX-Strahlzeiten\CU-beiA uswertung\, File: Online opj Worksheet: dat3_c, Grafikfenster: Graph5 rot: Differenz <110> Aarhus - 200µm blau: Differenz außerhalb Aarhus - 200µm 200 µm Kristall * 0.73 Difference Spectra Bent-Flat 1,0 Diff:Aa-200mu:<110> Diff:Aa-200mu:<U> 1,0 0,5 0,5 0, Energy [kev] 0, Energy [kev]

30 Events Direktory: C:x1messpc2\StrahlzeitdatenX-Strahlzeiten\CU-beiA uswertung\, File: Online new.opj Worksheet: dat3_c, Grafikfenster: Graph4 rot: Differenz <110> Aarhus - 200µm blau: Differenz außerhalb Aarhus - 200µm 200 µm Kristall * 0.73 Difference Spectra Bent-Flat 1,0 Diff:Aa-200mu:<110> Diff:Aa-200mu:<U> 0,5 0, Energy [kev]

31 Conclusions For Positron channeling a suitable machine is missing (Upgrading of BTF) Dechanneling length of Electrons have been measured 21.3 µm/gev With a 4 period Crystal Undulator an enhancement of radiation has been observed

32 B. Buonomo S.B. Dabagov G. Mazzitelli INFN Lab. Naz. di Frascati L. Quintieri J. Esberg Department of Physics and Astronomy Kim Kirsebom University of Aarhus Ulrik I. Uggerhøj H. Backe M. El-Ghazaly Institute for Nuclear Physics P. Kunz University of Mainz W. Lauth A. Rueda G. Kube DESY Hamburg