Wüstefeld et al., BESSY VSR , ICFA Workshop FLS, March 5-9, 2012, Jefferson Lab HZB, Berlin (Germany) Vision for the Future: BESSY VSR A V ariable Pulse Length S torage R ing* A. Föhlisch, A. Jankowiak, J.Knobloch, P. Kuske A. Neumann, M. Ries and G. Wüstefeld ICFA Workshop on Future Light Sources, March 5-9, 2012 Thomas Jefferson National Accelerator Facility, Newport News, VA (USA) * G. Wüstefeld et al., IPAC 2011
Vision for the Future: BESSY VSR A V ariable Pulse Length S torage R ing*. A. Föhlisch, A. Jankowiak, J.Knobloch, P. Kuske A. Neumann, M. Ries and G. Wüstefeld. HZB, Berlin (Germany). * G. Wüstefeld et al., IPAC 2011. - PowerPoint PPT Presentation
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G. Wüstefeld et al., BESSYVSR, ICFA Workshop FLS, March 5-9, 2012, Jefferson Lab
HZB, Berlin (Germany)
Vision for the Future: BESSYVSR
A Variable Pulse Length Storage Ring*
A. Föhlisch, A. Jankowiak, J.Knobloch, P. KuskeA. Neumann, M. Ries and G. Wüstefeld
ICFA Workshop on Future Light Sources, March 5-9, 2012Thomas Jefferson National Accelerator Facility, Newport News, VA (USA)
* G. Wüstefeld et al., IPAC 2011
G. Wüstefeld et al., BESSYVSR, ICFA Workshop FLS, March 5-9, 2012, Jefferson Lab
Outline
- MotivationBESSYVSR
2
- Expected results
- Long. bunch focusing by sc-cavities
- Current limit of short bunches: measurements & scaling laws
G. Wüstefeld et al., BESSYVSR, ICFA Workshop FLS, March 5-9, 2012, Jefferson Lab
why short e- bunches:- time resolved, picoseconds X-ray experiments- CSR for THz experiments
present situation at BESSY:- dedicated low- shifts, =3ps 4 blocks of 3 days per year, two operation modes: 40 mA (bursting) and 15 mA (stable)
Motivation
future goal: - simultaneously 15 ps & 1.5 ps bunch mode up to 100x more current in short bunches ( 10 000x more THz power)
3
G. Wüstefeld et al., BESSYVSR, ICFA Workshop FLS, March 5-9, 2012, Jefferson Lab
BESSY II synchrotron radiation source
number of cellsbeam currentnat. emittancenat. moment. spread
2x8<300 mA6 nm rad0.7x10-3
storage ring parameters
4 rf-cavities0.5 GHz , 1.5 MV
BESSY II ring1.7 GeV
240/ m
nat. bunch length0 = 13 ps (rms)
4
G. Wüstefeld et al., BESSYVSR, ICFA Workshop FLS, March 5-9, 2012, Jefferson Lab
Low- optics
- BESSY THz-optics short bunch, low current operation 15 ps 3 ps (rms) 700 fs are proven and analyzed- MLS – ring of PTB advanced, successful low- optics
good agreement between measurement and prediction single bunch current Ib/ mA
100.11E-21E-31E-4 1
bunc
h le
ngth
/
ps (
rms)
1
10
threshold fromcoasting beam
THzoptics
user optics
Ib3/7
measurements theory
- beyond bursting threshold bunches blow up in energy spread
8 nC
fixed rf voltage amplitude of 1.35 MV
- rule of thumb: (, Ib) (2, 5Ib)
6
P. K
uske
et a
l., P
AC 2
003
G. Wüstefeld et al., BESSYVSR, ICFA Workshop FLS, March 5-9, 2012, Jefferson Lab
Are short bunches limited to low currents ??
increasing the rf-gradient V’ x 100 can be increased x 100 I can be increased x 100
scaling law between and I predicted by:- Vlasov-Fokker-Planck simulation- bunched beam theory (Sacherer)- and coasting beam (Landau Damping)
/eEpΔpF |/nZ|I 0
0
||0
2)( I~
7
bunch length V'σ
I~V’for fixed
‘Keil-Schnell’:
recent papers:K.L.F. Bane, Y. Cai, and G. Stupakov, Phys. Rev. STAB 13, 104402 (2010)andY. Cai, talk, IPAC 2011
G. Wüstefeld et al., BESSYVSR, ICFA Workshop FLS, March 5-9, 2012, Jefferson Lab
CSR bursting measurements BESSY IIcomparison with theory, good agreement
8
threshold of instability forCSR of parallel metal plates
zero current bunch length caculated fromVoltage, and long. tuneVoltage range: 0.6MV – 1.8 MV
Scaling of CSR bursting threshold
Y. Cai, talk, IPAC 2011
scaled bunch length
scal
ed b
unch
cur
rent
BCS: =0.5+0.34+dip
scaled single bunch current A / MV
Nov. 2011
Jan. 2012
before 2003
BCS: =0.5+0.34+dip
rms b
unch
leng
th /
ps
coasting beamtheory
1086
4
2
1 1 10 100 1000
G. Wüstefeld et al., BESSYVSR, ICFA Workshop FLS, March 5-9, 2012, Jefferson Lab
BESSY II & sc-cavities
bunch length – current relationsc-cavities for bunch shortening
sc-cavities (scheme)100x enhanced rf-gradient
straight~ 5 m
cavity V1,f1 cavity V2,f2
9
->J. Feikes et al, EPAC 2006
G. Wüstefeld et al., BESSYVSR, ICFA Workshop FLS, March 5-9, 2012, Jefferson Lab
Simultaneously long & short bunches
- flexible fill pattern, I<300 mA- 15 ps & 1.5 ps pulses simultaneous at all beam ports- all IDs available
rel. long. phase position / ns
Volta
ge /
MV
0.5 GHz, 1.5 MV V’=Vxfrf= 0.75 MVGHz
long bunch
present nc-cavity (power)
10
1.75 GHz, 21.4 MVV’ = Vxfrf= 75 MVGHz
short & long bunches
sc-cavity # 1 & 2 (focusing)
sum voltage
short bunch
1.5 GHz, 25 MVV’=Vxfrf= 37.5 MVGHz
sc-cavity # 1 (focusing)
G. Wüstefeld et al., BESSYVSR, ICFA Workshop FLS, March 5-9, 2012, Jefferson Lab
MAD tracking
single particle tracking, BESSY II user optics & two sc-cavities
-300 -200 -100 0 100 200 300
-20 -10 0 10 20
rel. long. position / ps
rel. long. position / ps rel. long. position / ps
rel. long. position / psrel.
mom
entu
m /
0.00
1
40
20
0
-20
-40
40
20
0
-20
-40
rel.
mom
entu
m /
0.00
1
2
1
0
-1
-2
2
1
0
-1
-2
rel.
mom
entu
m /
0.00
1
rel.
mom
entu
m /
0.00
1
short & long bunchmomentumacceptance > +/- 4%
short & long bunchquantum excitation & damping10 damping times
4% 4%
0.7ps (rms)
short long
11
p/p acceptance
quantum limit
-20 -10 0 10 20
-300 -200 -100 0 100 200 300
G. Wüstefeld et al., BESSYVSR, ICFA Workshop FLS, March 5-9, 2012, Jefferson Lab
More advanced scheme: double beam
- double beam scheme combined with two sc-rf cavities
long and short bunches longitudinally and transversely separated
2 sc-rf cavities & low optics
long puls
short puls
2020 )pΔp()pΔp(1LL 00
chromatic orbit length:00pΔp 0
orbits of equal length L=L0: 2 solutions if =0, 1=0
double beam scheme
beam port
I) II)
12
20F0 /Δp/p
>0 <0
alternatively:short bunches are kicked on separate orbits, like the quasi-SB operationG. Portmann, et al., Proc. 2008 BIW, Tahoe City, CA (2008).
G. Wüstefeld et al., BESSYVSR, ICFA Workshop FLS, March 5-9, 2012, Jefferson Lab
photon beam image (beam port exit)
6cm
double beam can be easily produced at the MLS (low- optics)
good life time, high currents
transverse separation of photon beams
13
More advanced scheme: double beam
beam current: 170 mAlifetime: 10 h
e- beam, beam profile image
horizontal displacement
verti
cal d
ispla
cem
ent
measurements at MLS
G. Wüstefeld et al., BESSYVSR, ICFA Workshop FLS, March 5-9, 2012, Jefferson Lab
HZB expertise
BESSYVSRBERLinPro
14
BERLinPro and BESSYVSR: cavity design for BESSYVSR is similar to BERLinPro,1.3 GHz structures to be scaled to 1.5 GHz and 1.75 GHz
high current beam interaction with sc cavities to be studied at BERLinPro
-
-
G. Wüstefeld et al., BESSYVSR, ICFA Workshop FLS, March 5-9, 2012, Jefferson Lab
Summary
- 175 long bunches, 15 ps < 300 mA - 175 short bunches, 1.5 ps (rms) - at all beam ports available - all IDs available - present transverse user optics applied
bunch length (rms) / ps
current (sb) / mA
current (mb) / mA <300
present 350 bunch
fillingTHz optics
BESSYVSR
175 bunch filling
user optics
BESSYVSR
175 bunch filling
THz optics
3
0.04 (0.03 nC)
14
1.5
0.8
(140)
0.7 0.3
0.14 0.02
24 3.5
beamparameter
expected results:
long & short bunches simultaneously :
15
G. Wüstefeld et al., BESSYVSR, ICFA Workshop FLS, March 5-9, 2012, Jefferson Lab 17
G. Wüstefeld et al., BESSYVSR, ICFA Workshop FLS, March 5-9, 2012, Jefferson Lab 17
G. Wüstefeld et al., BESSYVSR, ICFA Workshop FLS, March 5-9, 2012, Jefferson Lab 21
MLS measurements
G. Wüstefeld et al., BESSYVSR, ICFA Workshop FLS, March 5-9, 2012, Jefferson Lab 22
Measurements from SPEAR3
J. Corbett et al.
G. Wüstefeld et al., BESSYVSR, ICFA Workshop FLS, March 5-9, 2012, Jefferson Lab 23
Measurements from DIAMOND
priv. comm. Ian Martin, DIAMOND
G. Wüstefeld et al., BESSYVSR, ICFA Workshop FLS, March 5-9, 2012, Jefferson Lab 26