Dafne Upgrade with large Piwinsky angle and crab waist

1
Dafne Upgrade with large Piwinsky angle and crab
waist

• P. Raimondi
• SLAC-Mac Oct.2006

2
Outline

• Dafne luminosity History
• Goals for the Finuda run
• Goals for the Siddarta run
• Mid-Long term plans

3
Luminosity history
4
DAFNE DELIVERED L IN YEAR 2004-5 for KLOE
109-111 bunches I-peak 2.05 A Ipeak 1.39
A Lpeak 1.53e32 cm-2s-1 Lday peak 9.9
pb-1 Lmonth gt 215 pb-1 L2004-5 gt 2200 pb-1
5
2006-7 goals

• Finuda Run Goal 1ft-1 by April 30, 2007
• - Start Oct-02 with cold check-outs
• - 1 month commissioning
• - 6 months data taking
• Siddartha Run Goal 1ft-1 by Dec 31, 2007
• - Install the new IR with cross-angle/crab-wai
  st and Siddartha detector (2-3 months)
• - start July-1st or Sept 1st
• - 1 month commissioning
• - 3 months data taking
• Dafne Goal 1033 By Dec 31, 2007

• LNF September 2006

6
Finuda Run

• Started on Oct-02
• Reestablished collisions, stored gt700mAmps e/e-
• Vacuum conditioning til Oct-31
• Better coupling correction wrt Kloe (just 2
  rotating quads instead of 4) 10
• Better e-ring impedance 20 (from shorter bunch
  and vertical emittance blowup)
• Better feedbacks gt10 (more current and more
  stable beams)
• Reduced wiggler field (-10)
• Reduced run duration
• 1.51032 by the end of the run, 0.2ft-1/month
  duable

7
Siddarta Luminosity

• New IR needed for Siddarta around mid-2007
• Very straightforward its design to overcome
  some of the present limitations and test the
  large crossing angle scheme
• No more parasitic crossing
• Very small vertical beta function
• Large Piwinsky angle
• Crab waist
• Fast kickers installed Better injection
  efficiency 50gt100
• No backgroundgt topping up
• Higher currents gt more luminosity (10)
• Wigglers pole modified to improve acceptance
• Longer lifetimes
• Less backgroung
• Higher integrated luminosity (10)
• Ti Coating in the e wigglers chambers
• Decreased e-cloud gt Higher e current, more
  luminosity (20)

8

• High luminosity requires
• - short bunches
• - small vertical emittance
• - large horizontal size and emittance
• to mimimize beam-beam
• For a ring
• easy to achieve small horizontal emittance and
  horizontal size
• Hard to make short bunches
• Crossing angle swaps X with Z, so the high
  luminosity requirements are naturally met
• Luminosity goes with 1/ex and is weakly dependent
  by sz

9
x
bY
e-
e
2Sx/q
q
2Szq
z
2Sz
2Sx
Crabbed waist removes bb betratron
coupling Introduced by the crossing angle

• Vertical waist has to be a function of x
• Z0 for particles at sx (- sx/2q at low
  current)
• Z sx/q for particles at sx (sx/2q at low
  current)
• Crabbed waist realized with a sextupole in
  phase with the IP in X and at p/2 in Y

10
Horizontal Plane
Vertical Plane
SuperB parameters Collisions with uncompressed
beams Crossing angle 225mrad Negligible
Emittance growth
11
Luminosity considerations
Ineffectiveness of collisions with large crossing
angle is illusive!!! Loss due to short collision
zone (say lsz/40) is fully compensated by denser
target beam (due to much smaller vertical beam
size!).
Number of particles in collision zone
No dependence on crossing angle! Universal
expression valid for both - head-on and crossing
angle collisions!
I. Koop, Novosibirsk
12
Tune shifts
Raimondi-Shatilov-Zobov formulae (Beam Dynamics
Newsletter, 37, August 2005)
Super-B
One dimensional case for ßy gtgtsx/?. For ßy ltsx/?
also, but with crabbed waist!
I. Koop, Novosibirsk
13
Crabbed waist optics
Sextupole lens
Anti-sextupole lens

g
-g
IP
?µxp ?µyp/2
?µxp ?µyp/2
Appropriate transformations from first sextupole
to IP and from IP to anti-sextupole
I. Koop, Novosibirsk
14
Normalised Luminosity vs x and y tunes
M. Zobov
Vertical Size Blow Up (rms) vs x and y tunes
With Crab Focus
Without Crab Focus
15
Beam size and tails vs Crab-waistSimulations
with beam-beam code LIFETRAC
Beam parameters for DAFNE2.
An effective crabbed waist map at IP
Optimum is shifted from the theoretical value
V1 to V0.8, since it scales like
szq/sqrt((szq)2sx2)
D.N. Shatilov, Novosibirsk
16
Synchrotron modulation of ?y (Qualitative
picture)
Head-on collision. Flat beams. Tune
shift increases for halo particles.
?y(z-z0)
Head-on collision. Round beams. ?yconst.
Crossing angle collision.Tune shift decreases for
halo particles.
z-z0
Relative displacement from a bunch center
Conclusion one can expect improvement for
lifetime of halo-particles!
I. Koop, Novosibirsk
17
M. Zobov
Present achieved currents L1.5e32
With the present achieved beam parameters
(currents, emittances, bunchlenghts etc) a
luminosity in excess of 1033 is predicted. With
2Amps/2Amps more than 21033 is
possible Beam-Beam limit is way above the
reachable currents
18
Wigglers off
SC Wigglers
SC Wigglers
Wigglers off
Dafne Wigglers
Dafne Wigglers
Very weak luminosity dependence from damping
time given the very small bb-blowup
M. Zobov
19
IR Layout

• No splitters (on both sides)
• Common beam pipe in QD0
• Separated beam pipes since QF1
• No dispersion in sextupoles due to splitters
• Needs new extremely simplified vacuum pipe (round
  everywhere, apart the y-one)
• Dipole fields need to be ajusted (Blong lower,
  Bshort higher) ? use splitters power supplies
• Doublets will be PM
• All the other elements (quads, sexts etc) are in
  place, need just to be moved nearby

20
IR layout
IP
QD0s
QF1s
M.Biagini
21
Siddarta
View of the modified IR1 region Similar
modifications will be made in the IR2, without
the low-beta insertion In addition in IR2 the two
lines will be Vertically Separate
22
Qf1s
QD0
Permanent SmCo quads already ordered (about 380K
for 6 quads) All other IR magnets and power
supplies reused Most of the Vacuum Pipes and
pumps reused New Vacuum pipes and pumps around
50K
23

• Dafne parameters for the Siddarta run

Np2.651010 I13mAmp110bunches Emix200nm
Emiy1nm Coupling 0.5 sigx200um
betx0.2m sigy2.4um bety6.0mm sigz20mm
crossing_angle225mrad L(110bunches,1.43A)1033
yy0.8/qxy crabbed waist shift
24
Optical functions and dynamic apertures
gt 20 sigma_x
gt 12 sigma_y full coupled
25
IR optics
bx1.4m by18.0mm Old betas
bx0.2m by6.0mm New betas
M.Biagini
26
Dafne 2008 and beyond

• If 1033 is achieved (or some above 51032) KLOE
  will start a new run with an upgraded detector.
• the only significant (in money) modifications on
  Dafne could be
• - Transfer lines mods to allow trickle
  injection
• - High Energy mods for NNbar experiment
• New Dipoles
• Possibly X-Band Linac in the transfer lines
  to allow on energy injection
• If the luminosity does not seems satisfactory,
  the only other possibility left (at the present)
  is the new machine DANAE, already at an advanced
  project state.

27
Dafne Goals Conclusions

• A new IR for Siddarta compatible with
  large-crossing angle option seems feasible
• Same IR can fit in KLOE(1 or 2)
• Predicted large luminosity boost based
  exclusively on pure back of the envelope
  geometric considerations, fully supported by
  extensive simulations
• 10 times more luminosity for a given current
  leads to a 10 times better luminosity/background
  ratio. Additional gain comes from the increased
  (about a factor 1.2) beam stay clear in the IR
• Possible to do top-of-the-line Accelerator
  Physics and RD for future factories (e.g
  SuperB)
• Simply rematching the IP betas, it will be
  possible to run like with KLOE 2004-5, with even
  larger beam stay clear across the doublet
• bx 0.2m gt 1.4m by 6.0mm gt 18mm