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Transcript
EMMA Design and Construction Bruno Muratori STFC, Daresbury Laboratory 21/01/09 The EMMA Project • EMMA (Electron Machine with Many Applications) is a design for a non-scaling FFAG – the world’s first • Collaboration of : BNL, CERN, CI, FNAL, JAI, LPSC Grenoble, STFC, TRIUMF • Part of BASROC (British Accelerator Science and Radiation Oncology Consortium) / CONFORM (COnstruction of a Non-scaling FFAG for Oncology, Research and Medicine) • Advantages: – Linear fixed field magnets: large dynamic aperture – Cheaper • Disadvantages: – Novel longitudinal & transverse dynamics – Rapid tune variations: multiple resonance crossings • Many potential applications – Driver for ADSR, µ acceleration, medical (e.g. PAMELA) INJECTION LINE ALICE to EMMA Tomography Section Screens x 3 (emittance measurement) Emittance measurement SRS Quadrupoles x 2 Vacuum valve Screen EMMA Ring SRS Quadrupoles x 3 Screen & Vert. Slit • New Dipole 30° & BPMs at dipole entrance Position measurement New Quadrupoles x 13 Match the probe beam to the requirements of EMMA Measure the properties of the probe beam ALICE Screen Wall Current Monitor Current measurement BPM Position measurement • Vacuum valve Ion Pump New Dipoles x 2 (33°) & BPMs at dipole entrance Position measurement Diagnostics – injection line • • • • • OTR Screen in ALICE before extraction dipole BPMs @ entrance of every dipole in injection line Straight ahead Faraday cup to measure charge & energy spread OTR screen in dogleg for bunch length & energy measurement Tomography section: 60 degrees phase advance per screen with three screens for projected transverse emittance measurements and profiles • Last dispersive section: – OTR screen & vertical slit in middle of first section together with – OTR screen in final section for energy and energy spread measurements – Vertical steerers for position & angle before ring (to be used with kickers for steering) – BPM at entrance of EMMA ring for position before entering ALICE to EMMA injection line (2) Tomography diagnostics also used to better control beam Different match for all energies (10-20 MeV) All matches achieved to good accuracy – wyaiwyg ‘what you ask is what you get’ Twiss parameters and dispersion and its derivative are different for every energy and have to be precise EMMA Ring Waveguide distribution IOT Racks (3) Injection Septum 65° Kicker Kicker Wire Scanner Extraction Septum 70° Screen Kicker Wall Current Monitor Septum Power Supply Kicker Power Supplies Cavities x 19 Screen Kicker Septum Power Supply Kicker Power Supplies D Quadrupole x 42 F Quadrupole x 42 Wire Scanner BPM x 82 16 Vertical Correctors 6 CELL Girder Assembly Location for diagnostics F Magnet D Magnet Cavity Ion Pump Girder 2 Cell Section (standard vacuum chamber) Field clamp plates Standard vacuum chamber per 2 cells Vertical Corrector Bellows BPM 2 per cell QD QF Cavity Location for diagnostic screen and vacuum pumping Injection & Extraction (1) Screen Septum Cavity Kicker Kicker Injection scheme shown Extraction is Kicker, Kicker, Septum arrangement Cavity Injection and Extraction (2) • • Have to match ‘orbits’ at all energy ranges & for all settings (10 – 20 MeV) – Kickers – Septum rotation & motion – In-house code (FFEMMAG - Tzenov) – Vertical & Horizontal steerers in injection line – also used for painting (3 mm rad acceptance) Kickers specified at 0.07 T EMMA Kicker Magnet Fast Switching Magnet length 0.1m Field at 10MeV (Injection) 0.035T Field at 20MeV (Extraction) 0.07T Magnet Inductance 0.25H Lead Inductance 0.16H Peak Current at 10/20MeV 1.3kA Peak Voltage at Magnet 14kV Peak Voltage at Power Supply 23kV Rise / Fall Time 35nS Jitter pulse to pulse >2nS Pulse Waveform Half Sinewave Applied Pulse Power Collaboration Design and construction of thyristor prototype units using magnetic switching and Pulse Forming Network techniques Kicker Magnet Power Supply parameters are directly affected by the compact design and require: • Fast rise / fall times 35 nS • Rapid changes in current 50kA/S • Constraints on Pre and Post Pulses Injection and Extraction • • • • Large angle for injection (65°) and extraction (70°) very challenging !! Injection/Extraction scheme required for all energies 10 – 20 MeV, all lattices and all lattice configurations Minimise stray fields on circulating beam Space very limited between quadrupole magnet clamp plates Final Parameters 25° Septum Concept Electrical feedthroughs (conductor path to power supply requires to be short to reduce inductance) 0 - 7° Translation & rotation in-vacuum bearings Motorised linear actuators external to vacuum Conductor connections with flexibility to feedthrough to accommodate septum movement • Complete septum assembly mounted from top section of vacuum chamber lid. • 2 linear actuators provide translation and rotation of septum. Vacuum flange Aluminium wire seal Pole gap 25 mm Septum Design • • • In house design of septum and vacuum chamber in progress Wire eroding of lamination stacks scheduled for February, steel delivered. Magnet measurements scheduled for April 09 Section view of septum in vacuum chamber ISO view of septum with vacuum chamber removed Plan view of septum in vacuum chamber Cavity Design 110 mm Cavity machined form 3 pieces and EB welded at 2 locations Parameter Frequency 1.3 GHz Input coupling loop Theoretical Shunt Impedance 2.3 M Realistic Shunt Impedance (80%) 2 M Qo (Theoretical) 23,000 (23000) R/Q 100 Ω Tuning Range -4 to +1.6 MHz Accelerating Voltage 120 kV 180 kV Total Power Required (Assuming 30% losses in distribution 90 kW 200 kW Power required per cavity 3.6 kW 8.1 kW Coolant channels Aperture Ø 40 mm Probe EVAC Flange Capacitive post tuner Normal conducting single cell re-entrant cavity design optimised for high shunt impedance Value Diagnostics / Extraction line spectrometer dipole ALICE SRS quadrupoles New quadrupoles TD Cavity EMMA NEW DIAGNOSTICS BEAMLINE LAYOUT SRS Quadrupoles x 6 New Quadrupoles x 4 Screen & Vert. Slit BPM & Valve Screen x 3 Tomography Section Emittance measurement Spectrometer Extracted momentum BPM @ dipole entrance Screen Faraday Cup Wall Current Monitor E-O Monitor Current measurement Longitudinal profile Location for Transverse Deflecting Cavity (NOT IN BUDGET) Screen ALICE New Dipoles (43°) & BPMs at dipole entrance Position measurement New Quadrupoles x 4 Diagnostic line deflecting cavity tomography EO spectrometer Measurements • Energy – First dipole & spectrometer at end with OTRs • Projected transverse emittance – Quadrupole scans & tomography 60° phase advance / screen – Equivalent set-up in injection line for comparisons • Bunch length – EO monitor downstream of the tomography section – No profile information • Possibility of introducing a transverse deflecting cavity (TDC) to measure additional bunch properties TDC Resolution (1) x deflecting voltage 0 x z σz screen deflector bunch L • In absence of quadrupoles resolution increases with distance (L) from TDC to screen TDC Resolution (2) deflecting voltage x z σz deflector screen bunch • In the presence of interspersed quadrupoles this is not so and we must take into account of the entire transfer matrix from TDC to screen – there can be as many quadrupoles as desired x1 R11 ' x1 R21 R12 x0 R22 x0' Transverse deflecting cavity (1) • Transfer Matrix to screen gives βd – deflector, βs – screen • Want R12 big → sinΔψ = 1, βs fixed → make βd large • Transverse displacement on screen is • Beam size on the screen Transverse deflecting cavity (2) deflecting cavity tomography EO spectrometer 1.6 1.35 0.95 1.13 Δµy = 65° Δµx = 90° Transverse deflecting cavity (3) • Reverse of formula gives requirement of cavity voltage N eV0 pcm0c z | sin cos | d 2 • Take Δµ = 65° and φ = 0 • For streaked bunch to be comparable to un-streaked bunch • βx,y = 9 m at the deflecting cavity therefore we need, assuming an emmitance degradation to 10 µm and a bunch length of 4 ps eV0 ≥ 0.23 MV @ 1.3 GHz • Equality gives a streaked beam which is √2 times un-streaked beam – only rough idea of requirements – not enough for ≥ 10 slices (what we would like) → ~ 1 MV ? – longer bunch lengths / better emittance → lower voltage Measurements with TDC • Slice emittance & transverse profiles given by – knowledge of R12 from TDC to screen R12 d s sin x1 R11 ' x1 R21 – one dimension on screen gives slice emittance – other dimension gives bunch length • Slice energy spread given by – streaked beam and spectrometer R12 x0 R22 x0' Milestones ALICE shutdown (Cable management installation) Diamond drilling of ALICE wall, cable tray installation 25 Oct – 21 Nov 2008 1 month Off line build of modules Oct 2008 – Jun 2009 9 months ALICE shutdown 1st Mar – 12th Apr 2009 6 wks ALICE shutdown 8th Jun – 13th Jul 2009 5 wks Installation in Accelerator Hall Mar – Aug 2009 6 months Test systems in Accelerator Hall May - Oct 2009 6 months Injection line and ring complete 31st Oct 09 Commission with electrons starting Nov 2009 Conclusions • • • • All components of injector line ordered (most already at DL) Order for Extraction / Diagnostic line to go out soon Very Challenging & exciting project ! Good characterisation of the beam at injection & extraction even without TDC • Have good location for TDC should it be used in the future – Realistic voltage parameters – Extra beam properties not available with EO – Currently looking at requirements for TDC with RF engineers • Aim to be commissioning with electrons at DL in November 2009 • Aim to demonstrate that non scaling FFAG technology works and compare results with the theoretical studies performed to gain real experience of operating such accelerators Acknowledgements • All the EMMA team – Internal staff – Collaborators