Accelerator Physics Studies for Generating Short Radiation Pulses at the Diamond Light Source - PowerPoint PPT Presentation

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Accelerator Physics Studies for Generating Short Radiation Pulses at the Diamond Light Source

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Thanks to M. Borland, K. Harkay (APS) SBSR05, INFN-LNF, 7 November 2005. 420 rad V kick ... Thanks to G. Wuestefeld (BESSY-II); M. Borland, K. Harkay (APS) ... – PowerPoint PPT presentation

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Title: Accelerator Physics Studies for Generating Short Radiation Pulses at the Diamond Light Source


1
Accelerator Physics Studies for Generating Short
Radiation Pulses at the Diamond Light Source
Introduction Short pulses low alpha optics Short
pulses crab cavities
  • R. Bartolini
  • Diamond Light Source Ltd

SBSR05, INFN-LNF, 7 November 2005
2
Diamond (July 2005)
SBSR05, INFN-LNF, 7 November 2005
3
Diamond nominal optics (working point 27.22,
12.36)
3 GeV Storage Ring (561.6 m) 24 cells DBA
lattice 18 short straights (5 m) 6 long straights
(8 m) emittance 2.7 nm ?y 1.5 m in short s. ?x
10 m _at_ injection point Qx 27.22 Qy
12.36 ?1 1.7 ? 104 ?2 1.9 ? 103 Lifetime
gt 10 h 7 beamlines in phase 1 (2007) Commissioning
2006
SBSR05, INFN-LNF, 7 November 2005
4
Low Alpha optics (I)
?z 2.83 mm (9.4 ps)
? 1.7?104 V 3.3 MV ?? 9.6 ?104
?z ? 0.3 mm (1 ps)
? (low_alpha_optics) ? 106
  • linear optics requirements

?x (_at_ injection) ? 10 m optic not too dissimilar
from nominal (?y in the straight sections lt 3
m) flexibility in the choice of the working point
(while keeping low ?) emittance can be relaxed
  • non-linear optics requirements

correct chromaticity AND ?2 while ensuring good
DA for injection off-momentum DA at least ?2 no
lifetime issues
SBSR05, INFN-LNF, 7 November 2005
5
Low Alpha optics (II)
? 106 Qx 21.22 Qy 12.36 ?x0 1.74 ?y0
-2.42 ?20 1.17?102 ?x 36.2 nm
? 106 Qx 30.22 Qy 12.36 ?x0 3.63 ?y0
-2.37 ?20 3.97?103 ?x 3.68 nm
LA_1
LA_2
SBSR05, INFN-LNF, 7 November 2005
6
Transverse dynamics for LA_1
Used three sextupole families to correct the
chromaticities and ?2 to zero One family had to
reverse the polarity (upgrade on the machine
needed)
  • other 5 sextupole families were used
  • to increase the on-momentum DA
  • On-momentum DA is barely acceptable (at least ?10
    mm in H are needed!)
  • to achieve ?2 off-momentum aperture with good DA

SBSR05, INFN-LNF, 7 November 2005
7
Off-momentum dynamics for LA_1
? 10 mm H DA is achieved up to ? 2 off momentum
DA for 2
SBSR05, INFN-LNF, 7 November 2005
8
Momentum Aperture for LA_1
Momentum aperture low alpha optics
Touschek Lifetime with 7 mm ID V gap 45 h for 10
?A in single bunch 6.2 mA in 2/3 filling (624
bunches)
Microbunch instability threshold
6D
Ib ? 1 ?A for ?z0 0.3 mm
4D
SBSR05, INFN-LNF, 7 November 2005
9
Low alpha optics Work in Progress
? 106 ?2 106 ?3 2?102
need to understand better the effect of higher
order terms in momentum compaction and the effect
of longitudinal to horizontal coupling
SBSR05, INFN-LNF, 7 November 2005
10
Crab cavities Zholents scheme
Thanks to M. Borland, K. Harkay (APS) SBSR05,
INFN-LNF, 7 November 2005
11
Analytical estimate of achievable compression
Assuming a linear RF slope, Gaussian beams and
linear compression, bunch length 10 ps the
minimum achievable x-ray pulse duration is given
by
Thanks to M. Borland, K. Harkay (APS) SBSR05,
INFN-LNF, 7 November 2005
12
Solutions with no lattice modification
4? in V
Crab cavities are located at 1.1 m from the
centre of the long straight
420 ?rad V kick
Thanks to M. Borland, K. Harkay (APS) SBSR05,
INFN-LNF, 7 November 2005
13
Modified lattice to allow for extra-space in the
long SS
4? in V
Crab cavities are located at 2.5 m from the
centre of the long straight The optics of a
superperiod is modified to restore the 4?
vertical phase advance between the crab cavities
Linear optimziation perforned with ELEGANT
Thanks to M. Borland, K. Harkay (APS) SBSR05,
INFN-LNF, 7 November 2005
14
Comparison of DA for modified lattice
on-momenutm DA is slightly reduced but still
about 20 mm in H
Thanks to M. Borland, K. Harkay (APS) SBSR05,
INFN-LNF, 7 November 2005
15
Comparison of momentum aperture for modified
lattice
Momentum aperture
Touschek lifetime 6D, 1 coupling, 7 mm ID gap
Nominal lattice 13.3 h Modified lattice 12.8 h
The effect of the crab cavity has to be included
(WIP)
Thanks to M. Borland, K. Harkay (APS) SBSR05,
INFN-LNF, 7 November 2005
16
RF parameters choice
  • compression is the same as long as hV is
    constant
  • choice of h is limited by the requirement of a
    linear chirp
  • choice of V is limited by the maximum deflection
    achieved and its impact on lifetime
  • Tracking studies with ELEGANT were performed to
    assess the RF voltage limits (zero length TM110
    cavity)
  • h6 (3 GHz) and 1.25 MV is acceptable a voltage
    of 1.5 MV generate particle losses in the
    vertical plane.
  • The maximum deflection is 400 ?rad

Thanks to M. Borland, K. Harkay (APS) SBSR05,
INFN-LNF, 7 November 2005
17
First analysis of emittance degradation
Tracking studies with ELEGANT to assess emittance
degradation showed no significant effect the
vertical and horizontal emittance
Thanks to M. Borland, K. Harkay (APS) SBSR05,
INFN-LNF, 7 November 2005
18
Crab cavities compression results
ELEGANT can simulate photon ray tracing and
optimize the parameter of the compression optics
to minimize the X ray pulse length
Achievable compression for different slit opening
and crab cavity voltage
Transmission for different slit opening and crab
cavity voltage
Thanks to M. Borland, K. Harkay (APS) SBSR05,
INFN-LNF, 7 November 2005
19
Crab cavities ongoing work
Looks feasible to get sub-ps x-ray pulses with
very good transmission Lattice asymmetry doesnt
introduce major problems Emittance degradation is
modest More simulations are needed to assess the
effect of lattice errors Impedance issues have
still to be addressed (machine impedance and HOM
in crab cavity)
Thanks to M. Borland, K. Harkay (APS) SBSR05,
INFN-LNF, 7 November 2005
20
Conclusions
  • Preliminary studies were carried out to
    demonstrate the feasibility of different schemes
    to generate short pulses in the diamond storage
    ring.
  • Low alpha optics with acceptable dynamic aperture
    was identified.
  • Crab cavities schemes are very promising and well
    suited to Diamond lattice
  • Thanks to G. Wuestefeld (BESSY-II) M. Borland,
    K. Harkay (APS).

SBSR05, INFN-LNF, 7 November 2005
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