The Mainz Microtron MAMI

Transcription

1 The Mainz Microtron MAMI Hans-Jürgen Arends Institut für Kernphysik Johannes Gutenberg-Universität Mainz

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3 Race-Track-Mikrotron D E out =z E L i+1 L i L 1 E λ coherence condition: (for lowest possible energy gain / turn) RTM 3 (180MeV - 855MeV) E = e c B 2π λ B=1.28T λ=0.1224m (2.45GHz) E=7.48MeV length: 9m

4 MAMI History 1975 Proposal for a Race-Track Microtron (design by Herminghaus et al.) 1979 First 14 MeV beam from the MAinz MIcrotron MAMI A First 183 MeV beam from MAMI A MAMI A operation with a total of 18,700 hours of beam time Development of 855 MeV MAMI B and Injector Linac 1984 Collaborative Research Center SFB 201 established (DFG) 1990 First 855 MeV beam from MAMI B MAMI B operation with a total of 88,500 hours of beam time 1999 SFB 443 established (DFG) 2000 Approval of 1.5 GeV Harmonic Double Sided Microtron (design by Kaiser et al.) Delivery and installation of the four 250 ton HDSM magnets 2006 first 1,5 GeV beam expected

5 Main Physics goals Study of the Structure of Hadrons at low momentum transfer non-perturbative regime CRC 443: Many Body Structure of Strongly Interacting Systems Deutsche Forschungsgemeinschaft (DFG)

6 Observables for inner Structure of Hadrons Spatial distribution of charge and magnetization: Form factors (electric and magnetic) - e scattering Response to electromagnetic field Polarizabilities - photon scattering Excitation spectrum Resonances electro and photo excitation

7 Electric Neutron Form Factor G e n

8 Proton excitation spectrum

9 A1:

10 Momentum resolution 12 C(e,e ) (10-4 ) Counts [10 3 ] Cg.s. 0 + (7.65 MeV) 1 (10.84 MeV) 1 + (12.71 MeV) 4 + (14.08 MeV) 1 + (15.11 MeV) 2 + (16.11 MeV) 2 (16.57 MeV) 1 + (19.69 MeV) 3 (9.64 MeV) 2 + (4.44 MeV) E * [MeV]

11 A2: Crystal Ball - TAPS combination Crystal Ball central detector 672 NaI crystals 80 MHz FADC electronics TAPS forward detector 528 BaF 2 crystals with veto counters particle ID via fast/slow scintillation light TAPS C B CB: prior service at SPEAR, DORIS, BNL

12 Nov '02: Crystal Ball moved from BNL to Mainz Nov '03: Crystal Ball installed at photon beam at MAMI Mar '04: forward wall (TAPS) and central detectors installed May '04: First tests with the complete setup June '04-Apr '05: First production runs

13 Detector performance: π 0 and η identification 2-γ events 6-γ events η 3π 0 6γ σ 25 MeV π 0 γγ σ 11 MeV η γγ σ 23 MeV

14 A4: Strangeness in the nucleon elastic e-n scattering with longitudinally polarized e-, => Parity violation d d d u u g u g g u s s A PV σ = σ R R σ + σ L L ~ M M NC PV EM ~ Q 2 ( ) M Z challenge für experiment and accelerator!

15 A4 - Experiment Cherenkov calorimeter 1022 PbF 2 crystals 100 MHz event rate fast electronics Q²=0.108: G Es + 0.1G Ms = Q²=0.23 : G Es G Ms =

16 Bonn Frozen Spin Target A4 Parity Violation Experiment

17 X1: Production and Application of X-Rays Set up for X-Ray Phase Contrast Transition Radiation foil stack 600 MeV e - e Photons(1/Electron 10-3 BW ) 1.5x x x10-5 Energy spectrum hω [kev] e - to beam dump Refraction Contrast Radiography TR chamber Microfocus σ Vert. = 0.5 µm σ Hor. = 19 µm 5 m object

18 Refraction Contrast Radiography Detector: X-ray film X-Ray Energy: ~20 kev (Polychromatic) Green Leaf (Ficus Benjaminus)

19 MAMI C: a fourth Race-Track-Microtron? E=855MeV E=1500MeV ( B = 1.28 T = const. ) t t

20 Double Sided Microtron (DSM) 250 t 250 t our solution 2000 to 2000 to K.-H.Kaiser et al. 250 t 250 t 43 turns, 855MeV 1,5GeV

21 Harmonic Double Sided Microtron (HDSM) E DSM /2 L 3 L 2 L 1 λ injection E DSM /2 coherence condition: e c B E = λ π 2 DSM e.g. B=1.3T λ=0.1224m (2.45GHz) E=41.8MeV length: 40m therefore: not possible λ=0.0612m (4.90GHz) E=20.9MeV

22 The Harmonic Double Sided Microtron (HDSM) for MAMI C No. 3 LINAC I (4.90GHz) No. 2 Extraction 1507MeV Matching-Section 4.90GHz B=1.539T max 43 turns 10m Injection 855MeV No. 4 LINAC II (2.45GHz) No. 1

23 Some pictures: Transportation and Installation of first magnet in accelerator hall (2001/02)

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25 Vacuum tubes and steering magnets 193 tubes ( harp ), 384 steering magnets

26 2.45 GHz Linac (5 sections, 5 klystrons) under vacuum, high power tested, fully operational

27 RF-System: The first two 4.90GHz Linac-Sections: prototype KPH The ready installed 2.45 GHz Linac prototype ACCEL

28 First injection: Sept. 28, 2006 MAMI - Tour on Wednesday 2007: 1.5 GeV beam for experiments

29 Status and Perspectives Test operation with beam: 2006 first tests in diagnostic pulse mode (very low beam power) up to max. energy of 1.5 GeV tests in cw-operation and high current (100mA) tests of all beam transfer systems (A1, A2, A4) From 2007 on: beam for experiments (test, data taking) variable beam extraction (in steps of ~15 MeV) optimal orientation of polarization in all experimental halls and at all energies

30 η N

31 New experimental equipment polarized frozen-spin target for Crystal Ball with linearly and circularly polarized photons Cryostat (Mainz-Dubna) first tests end of 2006

32 New experimental equipment polarized frozen-spin target for Crystal Ball with linearly and circularly polarized photons KAOS spectrometer for kaon detection K- electroproduction near threshold (elementary process) hypernuclei

33 Graphical impression of of the near future set-up KAOS spectrometer (GSI)

34 The detector packages for KaoS scintillators MWPCs talk of P. Achenbach fibre detector

35 Future plans - Overview A1- Collaboration (3-spectrometer setup, KAOS) Elm. formfactors (G en, G ep and G mp high precision) Generalized polarizabilities (VCS) - cont. 3 He structure studies and correlations Elementary Kaon electroproduction, hypernuclei A2- Collaboration (Crystal Ball &TAPS, frozen-spin target, recoil pol.) Helicity structure at higher energies Complete experiment in meson photoproduction (beam-target-recoil polarization) Magnetic moment µ of S 11 (1535) from γ p ηγ p η, η production (rare η, η decays, test of ChPT and C-invariance) Kaon threshold photoproduction In medium modification in γa ωx A4- Collaboration (e-scattering, PbF 2 calorimeter) Parity violating ep- scattering and transverse polarization at backward angles from proton and deuterium

36 hours 8000, ,00 MAMI Operation Time setup, tuning, development polarized unpolarized 6000, , , , , ,00 0, year In 2001: Half year shutdown for upgrading the beam transfer tunnel to 1.5GeV. 4277h of 4428h total in the first 6 months+2d = 97%

37 MAMI operational aspects Funding University of Mainz State of Rhineland-Palatinate Federal Government (DFG) } HBFG EU I3HP /Transnational Access Applications for: cluster of excellence, graduate school 200 physicists, international collaborators Belgium, Canada, France, Italy, Japan, Kroatia, Russia, Slovenia, The Netherlands, USA, Scotland Training researchers students