RCS design RCS design Valeri Lebedev AAC Meeting November 16-17, - PowerPoint PPT Presentation

RCS design RCS design Valeri Lebedev AAC Meeting November 16-17, 2009

Outline Outline • Objectives for RCS design • Logic behind parameter choices • Technical description AAC, November 16-17, 2009 – Valeri Lebedev 2

Objectives & Challenges Objectives & Challenges • Objectives – Beam acceleration from 2 to 8 GeV – Support • 2 MW in MI at 60 to 120 GeV (140 – 280 kW) • 8 GeV program with fast extracted beam ( ≥ 100 kW) – Look for a solution being less expensive than pulsed SC linac – Look into possible future upgrades p pg • Challenges – Beam current is ~5 times of Booster  Space charge, instabilities, RF, ep • Booster problems to be avoided Booster problems to be avoided – No transition crossing – No laminations seen by beam  smaller Z || , Z  – Zero Disp in cavities  No SB resonance Zero Disp. in cavities  No SB resonance AAC, November 16-17, 2009 – Valeri Lebedev Page 3

RCS Design Choices RCS Design Choices • Circumference, C = C MI /6 Energy, min/max, GeV Energy, m n/max, GeV 2/8 2/8 – 6 injections to fill MI 6 i j ti t fill MI 10 Repetition rate, Hz • High periodicity FODO Circumference, m (MI/6) 553.2 • Racetrack Tunes 18.43 – Two long straights g g T Transition energy, GeV siti G V 13.36 13 36 – Dispersion zeroing with Beam current at injection, A 2.2 missed dipole 98 Harmonic number • Acceptance matches MI acceptance Max. RF voltage, ( V 98 /V 196 ) MV g ( 196 ) 1.6/0.7 – 10% allowance for  growth 10% allowance for  growth 98 95% n. emittance, mm mrad 22 • 2 harmonics RF system Space charge tune shift, inj. 0.07† – Space charge mitigation Norm. acceptance, mm mrad 40 – Beam stability 4 3 4.3 Injection time for 1 mA, ms Injection time for 1 mA ms • High injection energy helps with • Hi h i j ti h l ith Linac energy cor. at inject. 1.2% Space Charge and Instabilities RF bucket size, eV s 0.38 – Small size of vacuum chamber † KV-like distribution, BF=2.2 AAC, November 16-17, 2009 – Valeri Lebedev Page 4

Optics Optics •  -functions are blown-up in injection region – reduction of foil heating – 6 half cells are used for injection region • Two types of quadrupoles with the same integral strength – Large aperture quads for injection & extraction g p q j Thu Sep 17 14:51:49 2009 OptiM - MAIN: - C:\VAL\Optics\MuonCollider\Synchrotron\RCS_withFoil_Inj.opt 40 1 BETA_X&Y[m] DISP_X&Y[m] 0 0 0 BETA_X BETA_Y DISP_X DISP_Y 276.616 Twiss parameters for the first half of the ring AAC, November 16-17, 2009 – Valeri Lebedev Page 5

Optics (continue) Optics (continue) • Straight line assignments – I j Injection, extraction, scraping ti t ti i – RF • Vacuum chamber radius, a = 21.3 mm (internal) – 7 mm allowance for orbit correction 7 mm allowance for orbit correction Thu Sep 17 14:55:45 2009 OptiM - MAIN: - C:\VAL\Optics\MuonCollider\Synchrotron\RCS_withFoil_Inj.opt 2.5 2.5 Size_X[cm] Size_Y[cm] 0 0 0 Ax_bet Ay_bet Ax_disp Ay_disp 276.616 Beam envelopes; acceptance -  n =40 mm mrad, E k = 2 GeV,  p/p = 5 x 10 -3 . AAC, November 16-17, 2009 – Valeri Lebedev Page 6

Vacuum Chamber Vacuum Chamber • Competing effects are – Shielding and distortion of dipole bending field by eddy currents excited in the vacuum chamber – Vacuum chamber stability under atmospheric pressure – Vacuum chamber heating by eddy currents Vacuum chamber heating by eddy currents – Transverse impedance due to wall resistivity – Ring acceptance • The compromise resulted in – Round stainless steel vacuum chamber with radius of a= 22 mm and wall thickness of d = 0.7 mm – Inside quads of injection and extraction regions: a =43 mm d = 1 mm – No limitations on the chamber thickness outside dipoles and quads No limitations on the chamber thickness outside dipoles and quads • Ring acceptances and beam emittance: – 85 mm mrad - limited by vacuum chamber size – 40 mm mrad – limited by scrapers – 22 mm mrad – 95% norm. beam emittance AAC, November 16-17, 2009 – Valeri Lebedev Page 7

Limitations on Vacuum Chamber Design Ch b D i • Shielding and distortion of the dipole bending field by eddy currents excited in the vacuum chamber     2 4 2 y ad        – Dipoles: |  B / B | max =8.5 x 10 -4 @16 ms B ( 0 , y ) iB 1 ... ,    y AC 2 2   12 240 a – Quads – approximately half of the dipole effect c c     a – Delayed quad wave form by ~70  s  2 ramp • Vacuum chamber stability under atmospheric pressure – Compression: 3.1 N/mm 2 p a  cmpr  P P – Bend for  a / a =0.02: 8.9 N/mm 2 atm d  2   9 a a   – Yield stress : 200 N/mm 2   P bend atm   4 a d • Vacuum chamber heating by eddy currents (~a 3 ) Vacuum chamber heating by eddy currents ( a ) – dP / dz =10 W/m   2 3 da dP ramp B  –  T =15 K for convective air cooling with 2 AC 2 heat transfer of 10 -3 W/cm 2 /K dz c AAC, November 16-17, 2009 – Valeri Lebedev Page 8

Vacuum Chamber Impedance I d • Transverse impedance due to wall resistivity (~a -3 ) 2 c  )  Z ( ( ) Z     0 0 2 2 3 3 4 a d – Z  and dP/dz are related inversely proportional    ad d • No dependence on vacuum  2 Z dP ramp B   2 0 c chamber parameters Z ( )      AC dz 4  2 2 10 Qf0 Z tr Laminated dipole [O/cm 2 ] 1 Solid dipole 0.1 0 1 Stainless steel 0.01 1 10 3 1 10 4 1 10 5 1 10 6 1 10 7 1 10 8 1 10 9               1 10 1 10 1 10 1 10 1 10 1 10 1 10 f [Hz] AAC, November 16-17, 2009 – Valeri Lebedev Page 9

Dipoles Dipoles • Small aperture Parameter Unit Value Number of magnets g 100  Compact dipole Peak field T 0.87375 Field at injection T 0.2184 • Sagitta – 1.7 cm Magnet gap mm 44 Good field area diameter mm 40 Field homogeneity 0.02 % Effective length m 2.13216 Peak current A 667 A Number of turns/pole 24 Copper conductor mm x mm 12.5 x 12.5 Conductor cooling hole diameter mm 7 N Number of pancake coils/pole b f k il / l 2 2 Lamination material M17 Lamination thickness mm 0.35 Inductance mH 25 DC resistance Ohm 0.021 Stored energy Stored energy kJ kJ 5.47 5 47 Av. Power losses (no eddy current) kW 4.3 Peak inductive voltage V 390 Number of cooling circuits/magnet 1 Water pressure drop MPa 0.5 Water flow l/min 2.8 Water temperature rise Cº 22 AAC, November 16-17, 2009 – Valeri Lebedev Page 10

Quadrupoles Quadrupoles • Large and small quads Parameter Unit Normal quad Large quad have the same field have the same field Number of magnets Number of magnets 122 122 8 8 integral Peak field gradient T/m 17.65 14.65 Field gradient at injection T/m 5.528 4.589 • Large quads Pole tip radius mm 25 45 Good field area diameter mm 40 75 – 4 in injection region Field nonlinearity (2D) 0.03 % 0.03 % – 4 in extraction region Effective length M 0.69 0.794 Peak current A 672 A Number of turns/pole 7 19 Copper conductor mm x mm 10 x 10 10 x 10 Conductor cooling hole diameter mm 5 5 N Number of coils/pole b f il / l 1 1 1 1 Lamination material M17 M17 Lamination thickness mm 0.35 0.35 Inductance mH 1.15 3.12 m  DC resistance 12 40 Stored energy Stored energy J J 260 260 700 700 Av. power losses (no eddy currents)) kW 2.0 6.7 Peak voltage V 40 110 Number of cooling circuits/magnet 1 4 Water pressure drop Mpa 0.5 0.5 Water flow l/min 1.9 1.6 Water temperature rise Cº 16 11 AAC, November 16-17, 2009 – Valeri Lebedev Page 11

Resonance Driving of Di Dipoles and Quads l d Q d • Dipoles and quads of each cell have a resonance circuit compensating their inductive impedance – 50 standard + 2 special cells (one for each straight line) • each is tuned to 10 Hz – Total power ~1.5 MW – Maximum voltage to ground 600 V • Similar to the Booster AAC, November 16-17, 2009 – Valeri Lebedev Page 12

Beam Acceleration Beam Acceleration AAC, November 16-17, 2009 – Valeri Lebedev Page 13

RF System RF System • Dual Harmonic RF system, – At injection V 2 =0.5 V 1 • 10 Bunches extraction gap – Set by required length of MI extraction gap • Beam loading is serious issue • Beam loading is serious issue – 1.6 MV beam induced voltage (at resonance) • Longitudinal emittance is blown up to ~0.6 eV s to match to MI RF bucket – Can be excited by quadrupole damper (same as in Booster) Can be excited by quadrupole damper (same as in Booster) 1-st harmonic 2-nd harmonic Harmonic number 98 196 Maximum voltage, MV 1.6 0.7 Minimum voltage, kV 20 10 Frequency sweep, MHz 50.33-52.81 100.66 – 105.62 Number of cavities 16 10 Shunt impedance, k  k  100 100 100 100 Sh t i d AAC, November 16-17, 2009 – Valeri Lebedev Page 14