Cooler Injector Synchrotron (CIS) at IUCF V.S. Morozov MEIC Collaboration Meeting March 30-31, 2015

MEIC Collaboration Meeting 3/30-31/152 Current MEIC baseline injector –Single 285 MeV 220  s pulse of 2.75  H - with low emittance IUCF Cooler Ring injector complex Introduction Optimum stripping energy: 13 MeV/u 10 cryostats 4 cryostats 2 Ion Sources QWR HWR IH RFQ MEBT 10 cryos 4 cryos 2 cryos

MEIC Collaboration Meeting 3/30-31/153 Put things in perspective –Get a feeling for parameter scales Compare CIS parameters to MEIC requirements Try to identify what the limitations are See if the performance can be improved Try to decide whether CIS or a similar system may be suitable for MEIC –Hardware may be available Learn from operational experience –Literature, particularly, X. Kang’s thesis and papers by D.L. Friesel et al. –Personal experience limited because there seemed to be no issues Request input from the audience on heavy ions Main Goals

MEIC Collaboration Meeting 3/30-31/154 Wide range of research: fundamental, material and medical science New injector complex replaced the 15 and 200 MeV cyclotron chain –Improve experimental luminosity –Simplify the injection process to increase the experimental duty factor Modest budget from NSF and IU of $3.5M in 1994 –New Linac, RF cavity, and ring magnetic, diagnostic and extraction systems –Surplus ion source, injection and extraction beam lines, and vacuum system Indiana University Cyclotron Facility

MEIC Collaboration Meeting 3/30-31/ mA (peak) unpolarized duoplasmatron source later replaced by high- intensity (>1 mA peak) Cooler Injector Polarized IOn Source (CIPIOS) Commercial 7 MeV 425 MHz H - /D - linac –3 MeV RFQ with replaceable vanes to accelerate D - to 4 MeV –4 MeV DTL Debuncher rotating longitudinal phase space to reduce momentum spread 200  s 300  A (peak) 7 MeV H - beam pulse at 4 Hz with 1  m normalized emittance and 150 keV FWHM energy spread Pre-Accelerator

MEIC Collaboration Meeting 3/30-31/156 Compact m 2.4 Tm ring with four-fold symmetry –One of the smallest and least expensive accelerators of this type Four 2 m 90  dipoles Four 2.34 m straights housing –Trim quadrupoles Tune and transition energy control –Strip injection equipment –Fast extraction equipment –RF cavity –Five vertical correctors (four dipole trim coils for horizontal steering) –Diagnostics x/y BPM pair at the entrance and exit of each dipole Large bandwidth wall gap monitor Ping tune kicker Removable wire Harp CIS Ring

MEIC Collaboration Meeting 3/30-31/157 Weak-focusing synchrotron Optics control –Dipole-straight length ratio –Dipole edge angles –Trim quadrupoles CIS Lattice

MEIC Collaboration Meeting 3/30-31/158 Working point chosen by adjusting dipole length and edge angles to avoid beam and spin resonances Trim quadrupoles can be used to control the betatron tunes Tune Diagram

MEIC Collaboration Meeting 3/30-31/159 Nominal transition energy is 256 MeV Trim quadrupoles provide the possibility of imaginary transition energy Transition Energy

MEIC Collaboration Meeting 3/30-31/1510 Fabricated from 1.5 mm modified 1006 steel laminations pre-coated with a B-stage epoxy resin (Remisol EB-540) –~4-6  m resin layer serves as an insulator and bonding agent –Sufficient to overcome the eddy currents at up to 5 Hz cycling rate Each dipole is made of 5 wedge-shaped and 2 endpack modules –Each module individually stacked, baked and machined –The modules mounted on a precision base plate assembly –Pole ends shaped to minimize the integrated sextupole component Main Dipoles

MEIC Collaboration Meeting 3/30-31/1511 Nominal natural chromaticities are low and do not require compensation The main sources of nonlinearity are sextupole fields –Sextupole component of the dipole field Minimized by endpack design –Sextupole component due to the eddy currents in the vacuum chamber wall Compensation using correcting coils Limiting the ramp rate Nonlinear Effects

MEIC Collaboration Meeting 3/30-31/1512 Correcting coils around the vacuum chamber inside the dipole –Correct the nonlinear field at the source Residual dipole field compensated using main dipole trim coils Compensation of Sextupole Component

MEIC Collaboration Meeting 3/30-31/1513 Frequency change from 1.3 to 10.1 MHz when accelerating from 7 to 200 MeV at h = 1 Support accelerator cycle rates of up to 5 Hz Non-uniform ferrite biasing: external magnetic field changes effective ferrite permeability –Wide tuning range –Small size RF Cavity

MEIC Collaboration Meeting 3/30-31/  s 300  A (peak) H - beam strip injected using 6 mm  25 mm 4.5  gm/cm 2 carbon foil –~400 turns at 0.48  s revolution period Three DC chicane dipoles produce a closed orbit bump near the foil and two bumper magnets kick the beam onto the foil during injection Intensity gain of ~80 achieved (~8  accumulated protons) Factors limiting the intensity –Scattering in the foil –Scattering on the residual gas of Torr –Slow fall time of ~200  s of the bumper magnets Strip Injection

MEIC Collaboration Meeting 3/30-31/1515 Beam adiabatically captured by ramping the RF cavity to 250 V in 2 ms Acceleration starts within a few  s of RF capture By the start of acceleration, due to short lifetime, stored beam reduced to < 2  protons –Well below space charge limit of ~ 2  protons Beam accelerated to MeV in 0.5 s –Dipole current and RF cavity frequency ramped using 96-step waveforms –No beam position feedback –Bunching factor varies from 3 at injection to about 5 at 225 MeV ~75% ramp transmission efficiency with a flattop intensity of ~1.1  –All losses occur in the first 200 ms of the ramp due to gas scattering Acceleration

MEIC Collaboration Meeting 3/30-31/1516 Bumper magnets and dipole trim coils used to locally bump the beam away from septum by -7 mm during acceleration and close to septum by +17 mm for extraction 1.3 m parallel-plate Blumlein kicker magnet supplies a 55 kV 300 ns voltage pulse across a 4 cm gap with a rise time of about 35 ns –20 mm beam displacement at the Lambertson septum entrance 1.1  out of 1.3  protons have been extracted at 200 MeV (85% efficiency) Extracted beam has emittance of ~10  m and momentum spread of about  2  Injection efficiency into the Cooler Ring of ~50% for both stacking and bucket to bucket transfer probably due to large emittance Fast Extraction

MEIC Collaboration Meeting 3/30-31/1517 With the demonstrated parameters of 1 Hz repetition rate and particles per pulse, assuming no injection losses, it would take about 4 and a half minutes to fill the MEIC booster, which is probably not practical On the other hand, assuming a 5 Hz ramp rate and an intensity closer to the space charge limit of 5  particles per pulse, filling the booster would take 11 s, which may be reasonable as long as this is a small fraction of the complete collider cycle Factors limiting the intensity –Vacuum pressure –Strip injection parameters, particularly, slow bumper fall time –Low RF cavity voltage –RFQ performance (from private communication with S.Y. Lee) –Possibly beam dynamics (need to look carefully at sextupole resonances) Need to think how to deal with heavy ions Conclusions