Perspectives for an energy increase of MAMI C

1. Perspectives for an energy increase of MAMI C Andreas Jankowiak Institut für Kernphysik Johannes Gutenberg – Universität Mainz 23.09.2008 Cristal Ball @ MAMI Collaboration Meeting

2. Present situation MAMI B • 855.3MeV, sE=0.013MeV (0.001%) • (883.1MeV maximum) • max. 103mA cw current • eh=8 nm rad, ev=0.5 nm rad • (allows for beam foci of ~mm) • Halo: < 10-5 at r > 5∙sr

3. Present situation MAMI C • 1508.4MeV, sE=0.100MeV (0.007%) • max. 100mA cw current (successful tested) • eh=12 nm rad, ev=2 nm rad • (measured, ev definitely overestimated)

4. What defines the end energy of an RTM: Eout=EInj+z•DE d magnet distance 2•R i+1 i 1 EInj (b1) DE dynamic coherence-condition: static coherence-condition: k,n: integer numbers

5. Increasing the end energy of an RTM: • increase B and adjust DE to full fill dynamic condition • adjust Einj to full fill static condition Energy increase by factor d means:

6. What defines the end energy of a DSM Einj dynamic coherence-condition: static coherence-condition: k,n=1: integer numbers Energy increase by factor d means (as for RTM):

7. 18 1600 16 1400 14 1200 12 10 1000 8 800 0 10 20 30 40 6 0 5 10 15 20 25 30 35 40 What defines the end energy of a HDSM In reality our machine (Harmonic Double Sided Microtron) is “a little bit more complicated” but the scaling is the same ! beam energy Energy gain per turn Eout=(1508.4±0.4) MeV total Bmax=1.539T linac I (4.90GHz) linac II (2.45GHz) Einj=855.11MeV Energy increase by factor d means (as for RTM):

8. Energy of the HDSM Therefore: Changing the maximum energy by factor d implies scaling of all machines by factor d (E and B fields) The maximum energy of RTM3 used so far is: 883.1MeV ! Ein=855.12MeV Scaling the HDSM by 883.1/855.3 (+3.25%) results in 1557.4MeV beam energy of the HDSM. Eout= 855.30MeV Ein Eout=180.03MeV Eout=1508.4MeV Ein Eout=14.86MeV Ein=3.97MeV

9. focussing defocusing Increasing the magnetic field of the HDSM dipoles remember: dipoles incorporates field gradient perpendicular to the pole face to compensate vertical defocusing necessary field accuracy: dB/B ~ 10-4 (bending angle errors, longitudinal beam dynamics)

10. Increasing the magnetic field of the HDSM dipoles HDSM dipole 03, field map (normalized to ideal field gradient, Bmax=1.539T for 1508MeV) without correction with correction

11. Increasing the magnetic field of the HDSM dipoles HDSM DIPOLE 02 at higher fields, more details 1508MeV 1.53T, without correction 1.53T with correction

12. Missing field: LINAC-Side Dispersions-Side s s Shim Shim Wedler Wedler Increasing the magnetic field of the HDSM dipoles (angle error ~ mrad) Correction with thin iron shim (designed for fields at 1.539T) and corrector magnet !

13. 1.539 T 1.539 T Increasing the magnetic field of the HDSM dipoles We measured field maps for all magnets at nominal field 1.539T = 1.508GeV (of course) 1.635T = 1.602GeV 1.708T = 1.674GeV 1602MeV 1.635T, without correction 1.635T with correction

14. surface correction plates corrector magnets shims Increasing the magnetic field of the HDSM dipoles corrector magnets system

15. Increasing the magnetic field of the HDSM dipoles corrector magnets system (design max values: horizontal 3mrad, vertical 2mrad @ 1.5GeV)

16. What does that mean ? First step (ca. 11/2008) (new colleague in our group, Robert Heine, will start 01.10.08 and will be in charge to study the possibilities of an energy increase) Inject 883.1MeV beam, increase HDSM magnetic field by 3.25% to 1.589T and klystron output power by 6.6%  HDSM = 1557.4MeV Could (should) work ! Will learn much about the behaviour of the dipoles! (excitation pattern of corrector magnets) This test is the basis for all further attempts ! drawback: e.g. strengths of power supply in transfer channel (to A1) is very near to the limit. Next steps: Depending on these results and their careful analysis !

17. What does that mean ? • Any further increase needs: • higher extraction energy from RTM3 and therefore complete • scaling of linac and all RTMs. • E.g. RTM3 dipole PS (609A, 310V) is at 582A@883MeV (96%)! • → limit for RTM3 Energy ~900MeV  1585.7MeV max. • We are currently checking all components concerning their • capabilities. • First look: 4 magnets ~ 95%@883MeV • injector linac klystron 100%@906MeV • 4.90GHz klystron 100%@1508MeV and 100mA • 100%@1600MeV and 50mA • proper adjustment (in advance by field measurements and magnet • cycling) of the relation of reverse field and main field of all • RTM dipoles (not possible just to scale, especially critical at RTM2) •  no simple knob for increasing Einj available • At certain energies it will require new hardware !

18. What does that mean ? Emax = 1600MeV need EInj=907MeV (13% increase in rf-Power) Emax = 1650MeV need EInj=936MeV (20% increase in rf-power) • new power supply for RTM3 dipoles, new injector linac klystron + PS • (what else ?) • new surface correction plates and shims • (needs to be designed based on already existing field maps • up to 1.708T = 1.674GeV, not clear if possible because • current line density in corners will dramatically increase) • their installation would need to dismantle most of the HDSM • hardware (4.90GHz linac, return path vacuum system, radiation • shielding ) • For high beam current operation: new 4.90GHz klystrons with • higher output power

19. Conclusion: • 1557MeV HDSM should be possible • (will be tested till end of 2008) • further exploration depending on results of test • - not simple and will most likely need new hardware • - at certain energy (my estimation between 1.560GeV and 1.6GeV) • new correction plates (very elaborate) necessary • - at certain energy klystrons will be at their limit • superconducting post accelerator • some basics • real estate gradient (cw): ~ 10 MV/m  100MeV needs 10m • cost: more expensive than HDSM (> 15Mio€) • no space where all experimental halls can benefit from increase