Post-LH Diagnostic Line for LCLS-II P. Emma, M. Woodley, Y. Nosochkov, Feb. 26, 2014
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Transcript of Post-LH Diagnostic Line for LCLS-II P. Emma, M. Woodley, Y. Nosochkov, Feb. 26, 2014
Post-LH Diagnostic Line for LCLS-IIP. Emma, M. Woodley, Y. Nosochkov, Feb. 26, 2014
Steal beam at 1-100 Hz with y-kicker after LH (Dy = 15 mm)Bend hor. 0.7 m with septum magnet and keep parallel to wallSuppress septum dispersion and add screen at x & y beam waist for easy emittance measurements (quad-scan or multi-screen)Final spectrometer (bend up) with screen and 3-W dumpHor. RF deflector provides time resolved y-emittance meas.Ver. RF deflector provides time resolved x-emittance (future)RF deflectors also provide absolute bunch length measurementsSpectrometer to measure projected and sliced energy spreadPanofsky-Wenzel energy spread needs to be <<5 keVCSR should not distort beam (easy in LH with long bunch)Chromatic effects need to be small (easy in LH, hard in BC1)Keep diagnostics beamline < 20 m (?)
e- dump(~3 W)RF deflectors
screen-2
9.4 mrad
0.8 m0.70 m
6.0
y
x
z
6.7 m
XDFYDF
z(plan view)
(elevation view)
HLAMKICKER HBND
2.0 m
wall
10.1 m
0.633 m
20
12 mm
0.8 m 0.5 m
1.74 m
0.5 m
screen-1future
Post-Laser-Heater Diagnostics Line Schematic(only very roughly to scale)
20.8 m
Dy = -6.3 mm to suppress hy
Rolled by 9.65 to suppress hy
100 Hz
Dy = -0.28 mm to suppress hy
Kicker – reduce inductance using several sections, each with a pulser
Kicker core (left) and full magnet (right), with 10 sections shown. Each core is driven by a separate pulser, but for clarity only one is shown here.
pulser (10-MHz capability?)Tony Beukers
Parameter Value Unit
Field 6.3 mT
Length 0.5 m
Kick angle 9.4 mrad
Pulsers & cores 5 -
Pulser voltage 500 V
Stability (rms) 0.01 %
magnetone core
OTR
2TCAVY
TCAVX
h y =
540
mm
spectrometer
x-dogleg
y-ki
cker
x-se
ptum
3 O
TRs
(120
)
Post-Laser-Heater Diagnostics Line
Thanks M. Woodley &Y. Nosochkov
Floor Coordinates
21.5 cm clearance (center-to-center)
6
Resolution Requirements
Resolve rms beam sizes of order ~30 mm to < 5%Deflectors should slice 1-mm bunch length into at least 10 bins (300 fs)Must resolve ½ of 5-keV heater energy spread (i.e., 2.5×10-5)Panofsky-Wenzel effect in TCAVX should be ¼ of 5-keV Use short (< 1 m) S-band RF deflector(s) – X-band not needed here
gex,y = 0.45 mmsE = 5 keVsz = 1.0 mmE = 100 MeVQ = 100 pC
2 TCAV’s OFF
37 mm
37 mm
SCREEN-1 (OTRB)
OTR
B
TCAVY
TCAVX (sy 110 mm) 377 mm
37 mm
TCAVY ON (0.5 MV)future
SCREEN-1 (OTRB)
sz
slice
-ge x
proj-gexpr
oj-ge y
400 mm
slice-gey 37 mm
TCAVX ON (0.5 MV)SCREEN-1 (OTRB)
sz
2 TCAVs OFFSCREEN-2 (OTR2)
34 mm
118 mm
OTR
2
TCAVY
TCAVX
h y =
540
mm
spectr.
TCAVX ON (0.2 MV)HEATER OFF (sE =0)
SCREEN-2 (OTR2)
21 mm
523 mm
1.0 keV PW syb 21 mm
sE
TCAVX ON (0.2 MV)HEATER OFF (sE =5 keV)
SCREEN-2 (OTR2)
34 mm
523 mm
sE
5.0 keV LH
CSR causes no issues
sE
5.0 keV LH
2 TCAVs OFFSCREEN-2 (OTR2)
sE
5.0 keV LH
TCAVX ON (0.2 MV)HEATER OFF (sE =5 keV)
SCREEN-2 (OTR2)523 mm
1.0 keV PW
TCAVX ON (0.2 MV)HEATER OFF (sE =0)
SCREEN-2 (OTR2)523 mm
sE
119 mm
1.0 keV PWsx = 110 mmV = 0.2 MV
f = 2856 MHz
TCAVX ON
269 mm 269 mm
269 mm
sdm (26 mm)/hy = 4.8×10-5 sdm (38 mm)/hy = 7.0×10-5
hy = 540 mmqy = 20
hy = 540 mmqy = 20
sd = 1.0×10-5 (PW) sd = 5.0×10-5 (LH)
hy = 810 mmqy = 30
hy = 810 mmqy = 30
sd = 1.0×10-5 (PW) sd = 5.0×10-5 (LH)
sdm (32 mm)/hy = 4.0×10-5 sdm (52 mm)/hy = 6.4×10-5
(eyby)1/2 = 20 mm
38 mm26 mm
52 mm32 mm
hy = 810 mmqy = 30
hy = 810 mmqy = 30
sd = 1.0×10-5 (PW) sd = 5.0×10-5 (LH)
sdm (16 mm)/hy = 2.0×10-5 sdm (45 mm)/hy = 5.6×10-5
(eyby)1/2 = 12 mm
Spectrometer at Low Charge (Q = 10 pC, gey = gex = 0.15 mm)
sE sE
45 mm16 mm
Chromatic Errors
0.05% rms energy spread (nominal)
0.20% rms energy spread (worst?)
Post-Laser-Heater Energy Spread at 95 MeV is 0.05% rms
No CSR Effects (100 pC, 1 mm bunch length)
(0.05% rms energy spread)
Linear energy-position correlations (dispersion) removed
5×10-5
qy = 30
6×10-5
Parameter symbol value UnitKicker length Lk 0.5 mKicker field Bk 0.0063 TKicker field regulation (7% jitter) (DBk/Bk)rms 0.01 %Vert. e- pos. at face of septum Dy 15 mmSeptum bend angle qx 6.0 degSeptum field Bs 0.043 TSeptum length Ls 0.8 mSeptum roll angle js 9.65 degBeam line hor. offset (wrt linac) Dx 0.7 mTCAVX (and TCAY) lengths Lxc,yc 0.8 mMax. crest TCAV voltage (S-band) Vx,y 0.5 MVSpectrometer bend length Ly 0.5 mSpectrometer bend field By 0.23 TSpectrometer bend angle qy 20 (30?) degQuadrupole lengths LQ 0.1 mQuadrupole pole-tip radius rp 16 mmMax. quadrupole pole-tip field Bp 0.12 T
Beamline Parameters
9-page PRD ready
L
hy
Quad focal length:
Chromatic aberration:
𝑓 ≈ 𝐿 /8Δ 𝜀𝜀0
≈ 12 ( 𝛽𝑓 )
2
𝜎𝛿❑2
𝐿≈8 𝛽𝜎𝛿
❑
√2 ( Δ 𝜀 /𝜀 )
Chromatic Limitation on Dog-Leg Length
Dog-Leg length:
b = 20 m, sd = 0.2%, De/e0 1%, L ≥ 2.3 m
b = 20 m, sd = 2.0%, De/e0 1%, L ≥ 23 m
Laser Heater:
BC1: