Study on the BC1 Energy Set Point

J. Wu working with T.O. Raubenheimer

LCLS-II Accelerator Physics meeting May 09, 2012

Study on the BC1 Energy Set Point

LCLS-II Accel. Phys. , J. Wu, SLAC

OUTLINE

Continue from the talk I gave on April 11, 2012Updated to LCLS-II design distance and also modeled the undulator resistive-wall wakefield effect and by-pass line wakefield effectPros of setting BC1 @ 300 ~ 350 MeV for LCLS-II

More accelerator tubes before BC1: lower the amplitude, avoid any breakdown related problem; more stable simply due to 1/sqrt(2) statistics; …

One concern about the chicane strength (looked into)More knowledge about the stability and tolerance (on-going)


LAYOUT: ACCORDING TO LCLS-II MAD DECK

BC1 @ 250 MeV

Set pointsBC1: R56 = 46 mm, Energy 250 MeV, peak current 176 AmpL1S: – 20 degreeL1X: – 160 degree; 19 MeVL2: – 31.4 degreeBC2: R56 = 29 mm, Energy 4.5 GeV, peak current 3 kA

BC24.5 GeV

By-pass13.5 GeV

TCAV3BC1250 MeV

L1S

wirescannerL1X

4 wire-scanners

L2-linac L3-linacDL1135 MeV

L0gun


UND

PROFILES

BC1END UNDBEG

CSR, LSC included in LiTrack, good agreement with Elegant [Bosch, Kleman, Wu, PRSTAB, 2008]


BC2 CSR AND L3 RF + WAKE

BC2END L3END



BY-PASS LINE AND UNDULATOR WAKE

Implement wakefieldUNDENDUNDBEG


LAYOUT: HIGHER ENERGY

BC1 @ 335 MeV

Set pointsBC1: R56 = 44.4 mm, Energy 335 MeV, peak current 207 AmpL1S: – 16 degreeL1X: – 160 degree; 30 MeVL2: – 32 degreeBC2: R56 = 27 mm, Energy 4.5 GeV, peak current 3 kA


BC24.5 GeV

By-pass13.5 GeV

TCAV3BC1355 MeV

L1S

wirescannerL1X

4 wire-scanners

L2-linac L3-linacDL1135 MeV

L0gun

UND

PROFILES

BC1END UNDBEG



BC2 CSR AND L3 RF + WAKE

BC2END L3END



BY-PASS LINE AND UNDULATOR WAKE

Implement wakefieldUNDENDUNDBEG



REMATCH THE OPTICS

Twiss-function through BC1 @ 335 MeV

EMITTANCE GROWTH

Due to ISR

E = 0.335 GeV; q = 6.43o; LB = 0.2035;DL = 2.44572; ;

Dgex = 5.5E-13 negligible

CSR and Space Charge: reported last time with Impact-T simulation small

25

1

T.O. Raubenheimer


BC1 DIPOLE FIELD INTEGRAL

BC1 energy set point to be as high as 350 MeV Assuming the set point range is from 200 MeV to 350 MeVAssuming the BC1 chicane can provide R56 from 15 mm to 65 mm for the above mentioned energy range (200 – 350 MeV)With the same geometry as in CDR

Then the maximum field integral of each dipole is 1.31 kG m (350 MeV and R56 of 65 mm)Details are plotted in the next page



BC1 DIPOLE FIELD INTEGRAL

BC1 energy set point: 200 -- 350 MeV BC1 chicane R56: 15 (red curve) – 46 (green curve) – 65 (blue curve) mm

1.31 kG m

1.10 kG m

SETPOINT

Comparison between setting BC1 @ 250 and 335 MeV

Next, look at the jitter and tolerance

BC1 Setpoint

(MeV)

Location R56,1

(mm)

L1S Phase (S-deg)

L1X Phase (X-deg)

L1X Amplitud

e (MV)

L2 Phase (S-deg)

BC2 Setpoint

(GeV)

R56,2

(mm)

250 11-2 46 -20 -160 19 -31.4 4.5 29

335 11-3 44.4 -16 -160 30 -32 4.5 27


L1S PHASE JITTER: UNDBEG CENTROID ENERGY

335 MeV250 MeV


L1S PHASE JITTER: UNDBEG RESIDUAL ENERGY CHIRP

335 MeV250 MeV


L1S PHASE JITTER: UNDBEG PEAK CURRENT

335 MeV250 MeV


L1X PHASE JITTER: UNDBEG CENTROID ENERGY

335 MeV250 MeV


L1X PHASE JITTER: UNDBEG RESIDUAL ENERGY CHIRP

335 MeV250 MeV


L1X PHASE JITTER: UNDBEG PEAK CURRENT

335 MeV250 MeV


L1X AMPLITUDE JITTER: UNDBEG CENTROID ENERGY

335 MeV250 MeV


L1X AMPLITUDE JITTER: UNDBEG RESIDUAL ENERGY CHIRP

335 MeV250 MeV


L1X AMPLITUDE JITTER: UNDBEG PEAK CURRENT

335 MeV250 MeV


INJECTOR TIMING JITTER: UNDBEG CENTROID ENERGY

335 MeV250 MeV


INJECTOR TIMING JITTER: UNDBEG RESIDUAL ENERGY CHIRP

335 MeV250 MeV


INJECTOR TIMING JITTER: UNDBEG PEAK CURRENT

335 MeV250 MeV



JITTER SENSITIVITIES AND TOLERANCE

250 MeV case from CDR

JITTER SENSITIVITIES AND TOLERANCE

335 MeV case on-going: L1S phase, L1X phase, timing

Jitter source EBC1 (MeV) DE/E0 (%) h0 (1/m) Dh (1/m) DI/I0 (%)

L1S phase (rms 0.06 degree)

250 0.01 10.08 1.88 3.53

335 0.01 -7.18 1.59 1.30

L1X phase (rms 0.50 degree)

250 0.01 10.14 5.44 2.63

335 0.02 -7.18 11.53 5.91

L1X amplitude (rms 0.05

MeV)

250 0.01 10.14 1.79 2.75

335 0.01 -7.18 0.14 1.22

Injector timing

(rms 200 fs)

250 0.02 10.14 0.98 2.92

335 0.01 -7.19 3.54 0.28



L1X PHASE JITTER

BC1@ 335 MeV: UNDBEG

L1X: -160.5o

L1X: -160o

L1X: -159.5o

Linear compression study with optimization for BC1 @ 300 -- 350 MeV up to undulator end

Longitudinal profile up to undulator end Tolerance study: centroid energy, residual energy chirp, peak

current on timing and LINAC phase jitter up to undulator entrance

Looked into BC1 dipole magnet design for BC1 @ 335 MeVo The maximum field integral of each dipole is 1.31 kG m

(350 MeV and R56 of 65 mm) Full machine lattice in Impact code is on going Strong focusing on sec. 11-2 More tolerance study is needed.

DISCUSSION


Documents

Study on the BC1 Energy Set Point