Transcript Accelerator F & DA

Accelerator
&
DAFNE crab waist experiment
M. Biagini, LNF-INFN
on behalf of the SuperB & DAFNE Teams
3rd International Workshop on
"B Factories and New Measurements"
Atami, Jan. 24th, 2008
Outline
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How to increase Luminosity?
The new collision scheme
SuperB beam-beam simulations
SuperB parameters, layout, lattice
DAFNE upgrade with new scheme
DAFNE commissioning status
Conclusions
SuperB Accelerator Contributors
M. E. Biagini, M. Boscolo, A. Drago, S. Guiducci, M. Preger, P. Raimondi, S.
Tomassini,
C. Vaccarezza, M. Zobov (INFN/LNF, Italy)
Y. Cai, A. Fisher, S. Heifets, A. Novokhatski, M.T. Pivi, J. Seeman, M. Sullivan,
U. Wienands (SLAC, US)
T. Agoh, K. Ohmi, Y. Onhishi (KEK, Japan)
I. Koop, S. Nikitin, E. Levichev, P. Piminov, D. Shatilov (BINP, Russia)
A. Wolski (Liverpool University, UK)
B. M. Venturini (LBNL, US)
S. Bettoni (CERN, Geneva)
A. Variola (LAL/Orsay, France)
E. Paoloni (Pisa University, Italy)
How to increase L ?
“Brute force” method
But...
 HOM in beam pipe
 Increase beam
currents
 Decrease by*
 Decrease bunch
length

overheating, instabilities,
power costs
 Detector backgrounds
increase
 Chromaticity increase

smaller dinamic aperture
 RF voltage increase

costs, instabilities
Hourglass effect
0,1
To
squeeze
the
vertical
beam by*
1 mm
dimensions, and increase L, by at IP
0,08
must be decreased. This is efficient
0,06
5 mm
only if at the same time the bunch
length is shortened to  by value, or
particles in the head and tail of the
bunch will see a larger by.
0,04
2 cm
0,02
s (m)
0
-0,02
-0,01
0
0,01
Bunch length
0,02
A new idea for L increase
P. Raimondi’s: to focus more the beams at IP and
have a “large” crossing angle  large Piwinski angle
 Ultra-low emittance
(ILC-DR like)
 Very small b* at IP
 Large crossing angle
 “Crab Waist” scheme
Test at DAFNE
now !!!
 Small collision area
 Lower b is possible
 NO parasitic crossings
 NO synchro-betatron
resonances due to
crossing angle
Large crossing angle, small x-size
1) Head-on,
Short bunches
sx
sz
Overlap region
(1) and (2) have same
Luminosity, but (2) has
longer bunches and
smaller sx
Vertical waist has to be a function of x:
Z = 0 for particles at –sx (- sx/2q at low current)
Z = sx/q for particles at + sx (sx/2q at low current)
2) Large crossing angle,
long bunches
sz
sx
Large Piwinski angle:
F = tg(q)sz/sx
y waist can be moved
along z with a
sextupole
on both sides of IP
at proper phase
bY
“Crab Waist”
... and ...
 Higher luminosity with
same currents and bunch
length:
 Beam instabilities are
less severe
 Manageable HOM
heating
 No coherent
synchrotron radiation
of short bunches
 No excessive power
consumption
 Lower beam-beam
tune shifts
 Relatively easier to
make small sx w.r.t.
short sz
 Parasitic collisions
becomes negligible
due to higher crossing
angle and smaller sx
IP beam distributions for KEKB
Beams are focused in the vertical
plane 100 times more than in the
present factories, thanks to:
- small emittances
- small beta functions
- larger crossing angle
Tune shifts and longitudinal
overlap are greatly reduced
KEKB
SuperB
I (A)
1.7
2.
by* (mm)
6
0.2
bx* (mm)
300
39
sy* (mm)
3
0.039
sx* (mm)
80
6
sz (mm)
6
5
L (cm-2s-1) 1.7x1034
IP beam distributions for SuperB
1.x1036
Here is Luminosity gain
Luminosity and blow-up vs current
Luminosity [cm-2 s-1]
Vertical Emittance Blow Up
2,5 10 37
3,5
2 1037
3
Gaussian Fit
rms
2,5
1,5 10 37
2
1 1037
1,5
5 1036
1
N
N
0
0
2,5 10
10
5 10
10
7,5 10
10
1 10
11
1,25 10
11
1,5 10
11
0,5
0
Horizontal Emiittance Blow Up
3 10
10
6 10
10
9 10
10
1,2 10
11
1,5 10
11
Longitudinal Emittance Blow Up
1,06
1,15
Gaussian Fit
1,04
1,1
rms
rms
Gaussian Fit
1,02
1,05
1
1
0,98
N
N
0,95
0
3 10
10
6 10
10
9 10
10
1,2 10
11
1,5 10
11
0,96
0
3 10
10
6 10
10
9 10
10
1,2 10
11
1,5 10
11
M. Zobov
Luminosity vs tunes scan
P. Raimondi, D. Shatilov, M. Zobov
0.64
0.62
0.6
0.58
0.56
• Individual contours differ by
10% in luminosity
• Design luminosity can be
obtained over a wide tune
area
0.54
0.52
0.5
0.5
0.52
0.54
0.56
0.58
0.6
0.62
0.64
(horizontal axis - nx from 0.5 to 0.65; vertical axis – ny from 0.5 to 0.65)
Transparency condition
 Due to the large crossing angle, new
conditions are possible, different from
asymmetric currents, for having equal tune
shifts with asymmetric energies
 LER and HER beams can have different
emittances and b* and equal currents


N
E
     
N
E


Present B-factories

b
E


     b  E

y

y
SuperB
b
E


  
 
b
E

y

y


LER beam:
• sees a shorter overlap region,
(4/7 of the HER one)
• has a smaller by*, easier to
achieve in the FF w.r.t. HER
• has larger emittance: better for
Touschek lifetime, and tolerance
for LER instabilities

E
s  s  b   b y
E


E
E




y   y , x   x
E
E

E
s x   s x
E

y

y

y
e-
e+
LER sz
HER sz
SuperB parameters (1)
 Present parameter set based on ILCDR-like
parameters
 Same DR emittances
 Same DR bunch length
 1.5 times DR bunch charges
 Same ILC-IP betas
 Crossing angle and “crab waist” to maximize
luminosity and minimize blowup
 Presently under test at DAFNE
 Use PEP-KEK DR damping time 19 ms
 No “emittance” wigglers used in Phase 1
SuperB parameters (2)
 ILC/FFTB like Final Focus
 Design based on recycling all PEP-II hardware,
Bends, Quads and Sexts, and RF system
 Corresponds to a lot of money !
 Maximize Luminosity keeping low wall power:
 Total power: 17 MW, lower than PEP-II
 Simulations performed in many labs and with
different codes:
 LNF,BINP,KEK,LAL,CERN
SuperB Parameters (Phase 1)
Circumference (m)
1800.
Energy (GeV) (LER/HER)
4/7
Current (A)/beam
2.
No. bunches
1342
No. part/bunches
5.5x1010
q (rad)
2x24
x (nm-rad) (LER/HER)
2.8/1.6
y (pm-rad) (LER/HER)
7/4
by* (mm) (LER/HER)
0.22/0.39
bx* (mm) (LER/HER)
35/20
sy* (mm) (LER/HER)
0.039
sx* (mm) (LER/HER)
10/6
sz (mm)
5
Power (MW)
17
L (cm-2s-1)
1.x1036
Transparency
conditions
Ring Layout
Length 20 m
Total length ~1800 m
Length 280 m
HER
No polarization
section here
Final Focus
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


Crossing angle to 2*25 mrad, L*=0.4 m
Local chromaticity correction
Horiz.beam separation at QD0: 2 cm, about 180 sx
A possible solution with a septum QD0, to avoid the
high background rate in the detector which would be
produced by the over-bend off-energy particles if a
dipolar component is present, is being studied.
 In the novel design, based on SC “helical-type”
windings, the windings generate pure quadrupole
field as a superposition of the inner field of the
surrounding coil and of the outer fringe field of the
neighbor one (Bettoni, Paoloni). Overall thickness ~
8mm, leaving about 60 sx of beam stay-clear.
IP layout
M.Sullivan
Example of QD0 design
S. Bettoni, E. Paoloni
Work in progress
0.3
0.2
By (T)
0.1
0
-2.0
-1.5
-1.0
-0.5
0.0
-0.1
-0.2
-0.3
x (cm)
0.5
1.0
1.5
2.0
Polarization
 Polarization of one beam is included in SuperB


Either energy beam could be the polarized one.
The LER would be less expensive.
 Long polarization times and short beam lifetimes
indicate a need to inject polarized electrons in
the vertical plane
 There are several possible IP spin rotators

Solenoids look better at present
 Expected longitudinal polarization at the IP of
about 87%(inj) x 97%(ring)=85%(effective)
J. Seeman, International Review Committee Meeting, LNF, Nov.07
DAFNE upgrade with “crab waist”
DAFNE Upgrade Team
D. Alesini, M. E. Biagini, C. Biscari, R. Boni, M. Boscolo, F. Bossi, B. Buonomo, A. Clozza, G.
Delle Monache, T. Demma, E. Di Pasquale, G. Di Pirro, A. Drago, A. Gallo, A. Ghigo, S.
Guiducci, C. Ligi, F. Marcellini, G. Mazzitelli, C. Milardi, F. Murtas, L. Pellegrino, M. Preger, L.
Quintieri, P. Raimondi, R. Ricci, U. Rotundo, C. Sanelli, M. Serio, F. Sgamma, B. Spataro, A.
Stecchi, A. Stella, S. Tomassini, C. Vaccarezza, M. Zobov (INFN/LNF)
I. Koop, E. Levichev, P. Piminov, D. Shatilov, V. Smaluk (BINP)
S. Bettoni (CERN, Geneva)
K. Ohmi (KEK)
N. Arnaud, D. Breton, P. Roudeau, A. Stocchi, A. Variola, B. F. Viaud (LAL/Orsay)
M. Esposito (Rome1 University)
E. Paoloni (Pisa University)
P. Branchini (Roma3 University)
M. Schioppa (INFN Gruppo di Cosenza)
P. Valente (INFN-Roma)
DAFNE performances
DAFNE Upgrade Parameters
DAFNE
FINUDA
DAFNE
Upgrade
qcross/2 (mrad)
12.5
25
x (mmxmrad)
0.34
0.20
bx* (cm)
170
20
sx* (mm)
0.76
0.20
FPiwinski
0.36
2.5
by* (cm)
1.70
0.65
sy* (mm)
5.4
2.6
Coupling, %
0.5
0.5
Ibunch (mA)
13
13
Nbunch
110
110
sz (mm)
22
20
L (cm-2s-1) x1032
1.6
10
Larger Piwinski angle
Lower vertical beta
Already achieved
DAFNE test expected results
 The upgrade of DAFNE run the new collision scheme will allow for peak
luminosities of 1033 cm-2 s-1
 The use of “crab waist” sextupoles will add a bonus for suppression of
dangerous resonances
 Brand new IRs layout and equipments have been designed, constructed
and installed
 This test will have the fundamental function of validating the simulation
(BBI code by K. Hirata)
Luminosity vs beam current
Luminosity vs tunes scan
Crab On  0.6/q
Crab Off
0.2
0.2
0.18
0.18
0.16
0.16
0.14
0.14
0.12
0.12
0.1
0.1
0.08
0.08
0.06
0.06
0.06
0.08
0.1
0.12
0.14
0.16
0.18
M. Zobov
0.2
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0.2
Strong-Strong Simulations
Single Bunch Luminosity
Crab Waist On
Crab Waist On
Crab Waist Off
tdamping = 30.000 turns
tdamping = 110.000 turns
x110 bunches = 1033 cm-2 s-1
(K. Ohmi, BBSS Simulations)
Hardware modifications
Interaction Region 2 (no collisions)
SIDDHARTA Setup
SIDDHARTA
QF1
Kaon monitor
Bhabha monitor
Lead shield
g monitor
Commissioning status (1)
 Rings closed end November
 First beams beginning of December
 Some BPMs problems due to new RF frequency
solved
 Maximum currents up to now 700/400 mA (e-/e+)
 Found pm quads lower gradient (2%) than
expected  rematched optics
 Coupling ~ 0.4/1.1% (e-/e+)
 Crab waist optics implemented, phase between
sextupoles OK
Commissioning status (2)
 Measured b-functions and dispersion in
agreement with model
 Collisions started at 200 on 200 mA (e-/e+), 60
bunches
 Measured vertical IP size: Sy = 8.1 mm
 Tuning of all subsystems in progress
 SIDDHARTA Detector will be installed first week
of February
Beam currents in 24 h
Conclusions (1)
 New large Piwinski angle scheme in SuperB will allow for
peak luminosity  1036 cm-2 s-1 well beyond the current
state-of-the-art, without a significant increase in beam
currents or shorter bunch lengths
 Use of “crab waist” sextupoles will add a bonus for
suppression of dangerous resonances
 Expected luminosity increase due to “Crab Waist” is:
a) a factor of 3, at least, for the DAFNE upgrade
b) about 2 orders of magnitude for the SuperB project
(with respect to the existing B-Factories)
 The principle is being tested at DAFNE
Conclusions (2)
 There is an international interest and participation in SuperB
 A CDR is being reviewed by the International Review
Committee
 In case of positive answer a TDR will be ready by 2010
 Next issues are: site, money, people
Upgraded DAFNE is in commissioning phase
Collisions at low current started
Results are expected very soon