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 SRS Quadrupoles x 2 Screen D ire ct io Screen & Vert. Slit m EMMA Ring Screen Wall Current Monitor Current measurement Be a Vacuum valve SRS Quadrupoles x 3 n Tomography Section Screens x 3 (emittance measurement Emittance measurement) BPM Position measurement • • Match the probe beam to the requirements of EMMA Measure the properties of the probe beam ALICE Vacuum valve New Dipole 30° & BPMs at dipole entrance Position measurement New Quadrupoles x 13 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 Me. V) 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 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 ction Beam dire
2 Cell Section (standard vacuum chamber) Field clamp plates Standard vacuum chamber per 2 cells Vertical Corrector Bellows BPM 2 per cell ction Beam dire QD QF Cavity Location for diagnostic screen and vacuum pumping
Injection & Extraction (1) Screen Septum Cavity Kicker Injection scheme shown Extraction is Kicker, Septum arrangement Cavity In je ct io n
Injection and Extraction (2) • • Have to match ‘orbits’ at all energy ranges & for all settings (10 – 20 Me. V) – 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. 1 m Field at 10 Me. V (Injection) 0. 035 T Field at 20 Me. V (Extraction) 0. 07 T Magnet Inductance 0. 25 H Lead Inductance 0. 16 H Peak Current at 10/20 Me. V 1. 3 k. A Peak Voltage at Magnet 14 k. V Peak Voltage at Power Supply 23 k. V Rise / Fall Time 35 n. S Jitter pulse to pulse >2 n. S 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 n. S • Rapid changes in current 50 k. A/ S • Constraints on Pre and Post Pulses
Injection and Extraction • • mm 133 al n inter • • Large angle for injection (65°) and extraction (70°) very challenging !! Injection/Extraction scheme required for all energies 10 – 20 Me. V, all lattices and all lattice configurations Minimise stray fields on circulating beam Space very limited between quadrupole magnet clamp plates Final Parameters 100 mm mm 180 al n inter 25°
Septum Concept Electrical feedthroughs (conductor path to power supply requires to be short to reduce inductance) 0 - 7° Motorised linear actuators external to vacuum Translation & rotation in-vacuum bearings m 5 m -7 to 1 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 k. V 180 k. V Total Power Required 90 k. W (Assuming 30% losses in distribution 200 k. W Power required per cavity 8. 1 k. W 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 3. 6 k. W
Diagnostics / Extraction line spectrometer dipole ALICE SRS quadrupoles New quadrupoles TD Cavity EMMA
NEW DIAGNOSTICS BEAMLINE LAYOUT New Quadrupoles x 4 SRS Quadrupoles x 6 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) deflecting voltage z σz screen deflector bunch L • In absence of quadrupoles resolution increases with distance (L) from TDC to screen
TDC Resolution (2) deflecting voltage 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
Transverse deflecting cavity (1) • Transfer Matrix to screen gives βd – deflector, βs – screen • Want R 12 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 • 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 e. V 0 ≥ 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 R 12 from TDC to screen – one dimension on screen gives slice emittance – other dimension gives bunch length • Slice energy spread given by – streaked beam and spectrometer
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 1 st Mar – 12 th Apr 2009 6 wks ALICE shutdown 8 th Jun – 13 th 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 31 st 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 theoretical studies performed to gain real experience of operating such accelerators
Acknowledgements • All the EMMA team – Internal staff – Collaborators
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