The MAinzer MIcrotron MAMI:

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1 The MAinzer MIcrotron MAMI: An cw Electron-Accelerator for Nuclear-Physics Andreas Jankowiak Institut für Kernphysik Johannes Gutenberg Universität Mainz March 2007

2 ~ 1975: strong demand for cw e - in the some 100MeV to GeV range to perform coincidence experiments (Lindenberger and Pinkau Ausschuß, Livingston Report, Barnes Report) nc-copper structure in cw-operation: ~ 15kW/m 2m The straightforward way to reach 800MeV: A long Linear Accelerator with -400 sections -ca. 1km length MW rf power (and at 100µA only 80kW for the beam, η~0.6%) Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 2

3 Possible solutions: Independent Orbit Re-Circulator Stretcher-Ring Linac 100MeV - ~GeV high energy gain / turn necessary (super conducting rf) low number of turns complex but flexible optics (achromatic, isochronous) excellent rf-amplitude and phase stability essential for good beam quality 100MeV - ~GeV Injektor high energies possible limited in average current somewhat limited in duty cycle (no real cw-operation) Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 3

4 The basis of our solution (H. Herminghaus) Race Track Microtron (RTM), normal conducting e.g.: single pass energy gain 7.5MeV, 90 turns 675MeV total energy gain and only 170kW for 67.5kW of beam power (100µA) η=40% Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 4

5 B=const. d E out =E Inj +z E magnet distance 2 R i i+1 R E = β e c B E= E max cos(ϕ s ) λ rf 1 E k rf z - ωt E Inj (β 1) static coherence-condition: dynamic coherence-condition: L 1 = k λ rf 2π (EInj + E) + 2 d = k λ e c B rf = n λ ( = 2π R) Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 5 L i+ 1 L i rf e c B E = 2π n λ rf

Ingredients: 1) strong longitudinal focussing E : reference particle E max n=1: -32.48 < ϕ s < 0............ ϕ s <0 k rf z - ω t Drift Lens Drift e.g. particle: arrives

6 Ingredients: 1) strong longitudinal focussing E : reference particle E max n=1: < ϕ s < ϕ s <0 k rf z - ω t Drift Lens Drift e.g. particle: arrives earlier, gains more energy has longer path lengths needs more time approaches reference particle Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 6

7 Examples (development of synchronous phase ϕ during acceleration) RTM1, MAMI: 4MeV 15MeV, 18 turns, E=0.6MeV, d=1.67m RTM2, MAMI: 15MeV 180MeV, 51 turns, E=3.24MeV, d=5.60m ϕ [ ] ϕ s = turn ϕ [ ] ϕ s = turn β in = / β in = β in = / β in = Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 7

8 i δep max ell δe [kev] 1i, 1000 ellreal 1i, (1) (2) Ψ Q (0) 1 = 10keV (4) e.g. ϕ s =-16, n=1 E=7.5MeV z=90 turns +500keV δep min 50 (3) φp min ell 0i, ellreal φp δφ 0i, max, [ ] rad rad Spur 1 Spur 2 Injection Extraction δφ=2-500kev Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 8

Ingredients: 2) simple scheme for transverse focussing beam outside midplane of the dipole experiences vertical defocussing in the fringe field of the dipole.

9 Ingredients: 2) simple scheme for transverse focussing beam outside midplane of the dipole experiences vertical defocussing in the fringe field of the dipole. v v B v reverse field stripes B fringe field B 0 reverse field z By adjusting the reverse field, vertical defocussing of the fringe field can be compensated or even vertical focussing can be introduced! Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 9

10 Ingredients: 2) simple scheme for transverse focussing Focussing (quadrupole singlets / doublets) only on linac axis! only few components focussing only in dispersion free region, no coupling of hor. and long. motion quadrupole doublet: 1/f doub ~ 1/f 2, focussing strength decreases with 1/E 2 increasing beta functions. e.g. horizontal beam ellipse RTM3 each 10th turn Due to pseudo damping of beam emittance during acceleration: 1 norm εx,y = εx,y β γ beam size stays nearly constant! Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 10

Ingredients: 3) dipole field homogenization by surface correction coils deflection errors / longitudinal dynamic requires: B/B 0 ~ 10-4 B=1G RTM3 Dip2 B/B

11 Ingredients: 3) dipole field homogenization by surface correction coils deflection errors / longitudinal dynamic requires: B/B 0 ~ 10-4 B=1G RTM3 Dip2 B/B 0 = without correction B=1G RTM2 Dip2 B/B 0 = with correction Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 11

The Mainz Microtron MAMI, scheme RTM 2 51 turns 180MeV B=0.55T 9 klystrons, 2.45GHz total power@100µa = 280kW E=7.5MeV ϕ s =-16 E=3.24MeV ϕ s =-16 B=0.10T E=0.6MeV ϕ s =-22 LINAC 3.

12 The Mainz Microtron MAMI, scheme RTM 2 51 turns 180MeV B=0.55T 9 klystrons, 2.45GHz total power@100µa = 280kW E=7.5MeV ϕ s =-16 E=3.24MeV ϕ s =-16 B=0.10T E=0.6MeV ϕ s =-22 LINAC 3.5MeV 100kV thermionic + photo gun (pol. e - ) beam parameters: 100µA max cw current (86kW beam power) injector linac: σe=1.2kev ( ) ε x,n = m rad RTM 1 18 turns 14.9MeV RTM 1: σe=1.2kev ( ) ε x.n = m rad RTM 3 max. 90 turns 180MeV-855MeV in steps of 15MeV RTM 2: σe=2.8kev ( ) ε x,n = m rad B=1.28T RTM 3: σe=13kev ( ) ε x,n = m rad ε x,abs = m rad *) Increase in energy spread and emittance due to sr-effects Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 12 *)

13 RTM tons, 1.28T, 90 turns 180MeV - 855MeV, 100µA Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 13

14 The Mainz Microtron MAMI, Floorplan (1999) 1988: commissioning of injector linac 1989: re-commissioning of RTM 1 06/1990: re-commissioning of RTM : first 855MeV beam MAMI B : first experiment starts (A2) 885MeV, σ E =0.013MeV (0.001%) max. 103µA cw current ε h =8 nm rad, ε v =0.5 nm rad (allows for beam foci of ~µm) Halo: < 10-5 at r > 5 σ r Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 14

15 Beam Diagnostic at MAMI: essential for fast machine setup Luminescence Monitor TM 110 -Cavity Monitor (ZnS-Screen, Position+Profile, Scanner (Position, non-invasive) invasive, very simple ) (Position+Profile, invasive) beam + Synchrotron Radiation Monitors (position + profile) + DCCT ( Förster-Sonde, current) on RTM3 linac axis + TM 010 -Cavity Monitor (Phase+Current, non-invasive) Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 15

angle x, y Linac-Axis SR-Monitor 10ns 10ns 0.

pulse mode for each turn) turn 1 90 1 90 x 1 y 1 x 2 y 2 ϕ I

16 Beam Diagnostic at MAMI: essential for fast machine setup automatic beam steering through RTMs corrector magnets, angle x, y Linac-Axis SR-Monitor 10ns 10ns 0.1ms TM 110 -Cavity Monitor, Position x,y turn (in diagnostic pulse mode for each turn) turn x 1 y 1 x 2 y 2 ϕ I Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 16

Beam Diagnostic at MAMI: very special Measurement of longitudinal phase space behind injector linac faraday-cup diaphragm cavity-deflector (16 khz-saw-tooth) horizontal phase video-in 3ps 408ps

17 Beam Diagnostic at MAMI: very special Measurement of longitudinal phase space behind injector linac faraday-cup diaphragm cavity-deflector (16 khz-saw-tooth) horizontal phase video-in 3ps 408ps sync-out dipole (50 Hz-saw-tooth) vertical energy bunched electron beam E Intra Beam Streak Camera φ TV-screen 1 deg = 1.13 ps Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 17

18 Specials: measurement and stabilization of beam energy Absolute energy calibration: using RTM3 dipole 1 as a spectrometer 2 R 9.80GHz TM 110 beam position monitor (well aligned with respect to linac axis) Measuring the average bending radius of turn 73 results in: ±140keV ( ± MeV (well defined position on linac axis and accurate measurement of beam position in turn No. 73) Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 18

Energy stabilization: E < E < E L < L < L RTM 3 9.80GHz TM 010 -resonator (λ=30.6mm) Time of flight measurement in the last 180 extraction turn via relative phase measurement between two 9.

19 Energy stabilization: E < E < E L < L < L RTM GHz TM 010 -resonator (λ=30.6mm) Time of flight measurement in the last 180 extraction turn via relative phase measurement between two 9.80GHz resonators (TM 010 ). By selecting a proper longitudinal Q-value it is possible to use this phase signal to steer the RTM 3 injection phase to stabilize the output energy! λ 2 rf 2 λ9.80ghz = = 8.16 mm/mev = 96 /MeV E 7.5MeV With a phase resolution of better 0.1 we get an energy stabilization of: ~ 855MeV = GHz Cavities (free aperture 8mm): 18 / 32 / 44 / 52 / 90 turn 315 / 420 / 510 / 570 /855 MeV Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 19

20 MAMI B operation hours Operation Time [h] 8000, , , , , ,00 Half year shutdown setup, for tuning, upgrading the beam polarized transfer development tunnel to 1.5GeV. unpolarized 4277h of 4428h total in the first 6 months+2d = 97% , ,00 Total of 90026h of operation (since 1991)! 0, Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 20 year 1999: Approval of the MAMI C project! HDSM (855MeV 1.5GeV) as fourth stage of MAMI B

21 Why and How MAMI C 1999: new Collaborative Research Center SFB443 Many body structure of strongly interacting systems need for cw beam with E=1.5GeV but: preservation of the excellent beam quality of MAMI B machine shutdowns as short as possible no new buildings therefore: simple and reliable technology make use of the Institutes expertise and installations (normal conducting rf-systems and iron core electromagnets) Decision to add a fourth stage realising MAMI C Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 21

A Race-Track-Microtron? E=855MeV E=1500MeV ( B = 1.28 T = const. ) 1.8 5.8 1.

22 A Race-Track-Microtron? E=855MeV E=1500MeV ( B = 1.28 T = const. ) t 2000t Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 22

23 Double Sided Microtron (DSM) 250 t 250 t our solution 2000 to 2000 to 250 t 250 t 43 turns, 855MeV 1,5GeV Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 23

24 dynamic coherence condition of a DSM: per magnet R i+1 R i E = λ e c B π 2 2π (Ri+1 - R i ) - 4 (R i+1 - R i ) 4 = 2 (π-2) R=2 λ phase advance / turn must be 2 2π in a DSM! e.g.: B=1.28T, λ=0.1224m (2.45GHz) E=41.1MeV (with cw-sections: linac ~ 45m) Therefore here: λ DSM = m E=20.5MeV (linac ~ 20m) The fundamental frequency of the HDSM must be 4.90GHz instead of 2.45GHz! Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 24

25 Specials (i): field gradient compensation of fringe-field defocusing? 45 entry and exit angle top view side view Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 25

26 Specials (i): field gradient compensation of fringe-field defocusing! 45 entry and exit angle dipole with field-gradient B y [T] 1,6 1,5 1,4 1,3 1,2 1,1 1,0 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0,1 0,0 B max =1.539T focussing defocusing Polschuh-Kante 60% B max -0,4-0,2 0,0 0,2 0,4 0,6 0,8 1,0 1,2 z [m] F B (force F normal to magnetic field B) Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 26

27 Consequences of the field gradient for the longitudinal dynamic: synchronous energy gain / turn [MeV] 17,0 16,5 16,0 15,5 15,0 14,5 14,0 13, Turn [#] With increasing energy the beam intrudes deeper and deeper into the 90 dipoles and experiences, compared to a homogenous dipole, turn by turn a relatively decreasing field-integral, which requires less energy gain per turn to fulfil the dynamic coherence condition. Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 27

28 Consequences of the field gradient for the longitudinal dynamic: Q= 1/2 1/3 1/4 1/5 1,05 1/6 1,00 0,95 0,90 0,85 0,80 0, Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 28 ϕφ 0 stop band when certain phasing error between linac 1 and linac 2

29 Scheme of longitudinal bunch positions in a DSM (remember: sub-harmonic injection with 2.45GHz in a 4.90GHz rf-system) λ DSM l 1 =23 (2x11.5) l 2 =25 (2x12.5) (in units of λ DSM ) λ DSM λ=2 λ DSM 2 Linacs operating at ν 1 =4.90GHz and ν 2 =2.45GHz Harmonic Double Sided Microtron (HDSM) Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 29

30 Specials (ii): harmonic operation 1,2 1,1 1,0 0,9 0,8 0,7 0,6 0,5 0,4 0,3 less steep gradient of 2.45GHz wave avoids reaching instable area HDSM one 4.90GHz linac + one 2.45GHz linac DSM 0,2 LINACI 0,1 LINACII 0, Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 30 φ 1,2 2 times a 4.90GHz linac instable region of longitudinal motion for 4.90GHz wave

31 Harmonic-operation (highest longitudinal beam stability) δe [kev] DSM, 2 x 4.90GHz linac longitudinal phase-space DSM Longitudinaler Phase-Raum DSM linacs φ=3 φ=3grad error (relativ (relative zu 4.90GHz) to 4.90GHz) Injektion -250 Extraktion ,0-1,5-1,0-0,5 0,0 0,5 1,0 1,5 2,0 δφ [Grad] δe [kev] HDSM, 4.90GHz GHz Linac longitudinal phase-space HDSM linacs φ=5 error (relative to 4.90GHz) Longitudinaler Phase-Raum HDSM φ=2.5grad (relativ zu 2.45GHz) Injektion Extraction ,0-1,5-1,0-0,5 0,0 0,5 1,0 1,5 2,0 δφ [Grad] Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 31

32 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 Best adaptation to the inherent stable and reliable RTM principle Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 32

Magnet as it is: B/B ~ 10-3 (in the central area: ~10-4, excellent manufacturing quality) required is: B/B ~ 10-4 measurements

33 90 bending dipoles, some photos transport and installation of all four magnets (finished in 2002) power supplies by: measurement of the magnetic field of all 4 magnets to get the data for the construction of surface correction coils! Magnet as it is: B/B ~ 10-3 (in the central area: ~10-4, excellent manufacturing quality) required is: B/B ~ 10-4 measurements finished: 09/2003 correction coils ready and checked, magnets final assembled: 03/2006 Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 33

34 Surface correction coils, some photos All pairs of surface correction coils for all 4 dipole magnets are manufactured, tested and ready for installation. Manufactured by water-jet cutting out of Al-plates Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 34

is applied Andreas Jankowiak, Institut für

35 Field correction: HDSM DIPOLE 02 left without correction right without correction with correction with correction at the edges some further correction by iron shims is applied Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 35

36 Vacuum-system, some photos 7m Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 36

37 2.45GHz linac + rf-system klystrons (5 x TH2174, 50kw cw) linac sections (5 x MAMI B type, 33ACs, 72MΩ/m) INP/MSU + aside some modification and modernisation: copy of RTM3 linac ready installed, under vacuum, power tested (08/2005) Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 37

operation since (12/2006) matching section installed all klystrons in house (5 + 4 spare) long-term

38 4.90GHz linac + rf-system linac sections (8 x, in house development, 35ACs, 80MΩ/m) + PMB (France) klystrons (4 x TH2166, 55kw cw) all 13 sections in house and power tested (02/2006) linac ready for operation since (12/2006) matching section installed all klystrons in house (5 + 4 spare) long-term sales agreement with THALES 1m Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 38

39 2.45GHz and 4.90GHz sections manufactured by ACCEL 2.45GHz section 4.90GHz section Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 39

40 In 12/2006 Beam tests in diagnostic pulse mode Only some vacuum tubes of extraction system are missing Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 40

Intensity signal of low-q rf-intensity monitor on the axis of the 2.45GHz and 4.90GHz linacs 2.45GHz linac turn 1 19.12.2006 (after 8h of operation) 4.

41 Intensity signal of low-q rf-intensity monitor on the axis of the 2.45GHz and 4.90GHz linacs 2.45GHz linac turn (after 8h of operation) 4.90GHz linac turn 43 RTM 3 855MeV 1508MeV The intensity signals of the two linacs are interleaved. The drop in amplitude is partly related to beam losses, but also due to the phase advance the beam experiences during the acceleration process in both linacs. Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 41

Intensity signal of low-q rf-intensity monitor on the axis of the 2.45GHz linac 20.12.2006 turn 1 turn 43 2.

42 Intensity signal of low-q rf-intensity monitor on the axis of the 2.45GHz linac turn 1 turn GHz linac RTM 3 855MeV 1508MeV After transverse beam matching the drop in amplitude is now dominated by the phase advance the beam experiences during the acceleration process. Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 42

19.12.2006, beam not good matched, beam losses observed!

2006, beam good matched, no beam losses observable (with the available

43 , beam not good matched, beam losses observed! turn MeV turn 1 855MeV , beam good matched, no beam losses observable (with the available diagnostics) turn MeV turn 1 855MeV Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 43

44 Longitudinal dynamics after optimisation: simulation versus measurement (the parameters of the simulation are fitted to the measured data) Φ1 i ΦM1 i Φ2 i ΦM2 i GHz Linac simulation / measurement 4.90GHz Linac simulation / measurement Fitting the simulation parameters by comparison of measured and simulated phase advances results in the following parameter set (design parameters in brackets): E INJ = MeV ( MeV) turn 1-43 φ 4.90GHz = ( ) / E max.,4.90ghz =9.021MV (9.052MV) φ 2.45GHz = ( ) / E max.,2.45ghz =9.399MV (9.298MV) Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 44

45 Since : User operation 1.508GeV / 10µA, polarized beam (83%) Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 45

46 User operation A1 (the first 10 day run): 1.508GeV, 10µA, polarized beam ( 83%) short high current test: 50µA (75kW beam power) beam on target: >80% Fr., , till Mo., , Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 46

47 MAMI C beam parameters 1508MeV, σe=0.100mev max. 100µA εh~10 nm rad, εv~0.5 nm rad as MAMI B! MAMI B beam parameters (in operation since 1990) 885MeV, σe=0.013mev (0.001%) max. 103µA cw current εh=8 nm rad, εv=0.5 nm rad (allows for beam foci of ~µm) Halo: < 10-5 at r > 5 σr ca. 6000h 7000h operation / year Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 47

48 Why all this: Many body structure of strongly interacting systems 1 nucleon (proton, neutron)? 2 E out, p out, S ou E in, p in, S in Well known electron beam: E=854.5MeV ± 0.013MeV (0.0015%) I= ~ pa 100µA 3 E i, p i, S i From it is possible to determine? Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 48

49 For orientation: floorplan RTM1+Inj. Linac Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 49

For orientation: Birds Eye View: RTM 1 + 2 RTM 3 The accelerator and experimental areas are 10m to 15m below surface

50 For orientation: Birds Eye View: RTM RTM 3 The accelerator and experimental areas are 10m to 15m below surface and behind 2m to 3m of concrete! Andreas Jankowiak, Institut für Kernphysik, Johannes Gutenberg Universität Mainz 50

The Mainz Microtron MAMI

The Mainz Microtron MAMI Hans-Jürgen Arends Institut für Kernphysik Johannes Gutenberg-Universität Mainz Race-Track-Mikrotron D E out =z E L i+1 L i L 1 E λ coherence condition: (for lowest possible energy