Transcript PEP-II Status and Outlook John T. Seeman For the PEP-II Team SLAC EPAC Meeting June 12, 2003

PEP-II Status and
Outlook
John T. Seeman
For the PEP-II Team
SLAC EPAC Meeting
June 12, 2003
PEP-II e+e- Collider
•
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PEP-II is a two ring e+e- asymmetric collider
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PEP-II Run for FY2003
• Turned on November 15, 2002, after a 3.5 month down.
• Storms in December caused power outages and component
damage.
• Winter-spring run is going well, in general.
– Exceptions: three IR vacuum leaks, lost a 1.2 MW klystron,
many RF trips (aborts) (but getting better), many HER IR
“dust” events causing radiation aborts.
• Integrated luminosity is on track reaching a total of 135 fb-1.
• Luminosity is increasing with new records every few weeks.
• Will turn off PEP-II on June 29.
• Will turn on September 8, 2003 for a ten month run.
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Recent Accelerator Advances
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By-3 bunch pattern has worked well.
Orbit bumps in sextupoles helps coupling.
Shorter abort gap (2.5%) works helping RF transients.
Three LER RF stations and six HER RF stations in use
– Didn’t get HER 7th station on line.
• Moved horizontal tunes to the half integer.
• LER horizontal beta-beats much better.
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PEP-II Monthly Peak Luminosity
Peak PEP-II Luminosity (x1E33) per Month
7
6
5
4
3
2
1
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Jun-03
Dec-02
Jun-02
Dec-01
Jun-01
Dec-00
Jun-00
Dec-99
Jun-99
0
8
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Apr-03
Jan-03
Oct-02
Jul-02
Apr-02
Jan-02
Oct-01
Jul-01
Apr-01
Jan-01
Oct-00
Jul-00
Apr-00
Jan-00
Oct-99
Jul-99
Apr-99
Jan-99
pb-1
PEP-II Daily Int. Luminosity
PEP-II Daily Average for each Month
300
250
200
150
100
50
0
9
0
Jan-99
Mar-99
May-99
Jul-99
Sep-99
Nov-99
Jan-00
Mar-00
May-00
Jul-00
Sep-00
Nov-00
Jan-01
Mar-01
May-01
Jul-01
Sep-01
Nov-01
Jan-02
Mar-02
May-02
Jul-02
Sep-02
Nov-02
Jan-03
Mar-03
May-03
pb-1
PEP-II Integrated luminosity
PEP-II Monthly Integrated Luminosity
8000
7000
6000
5000
4000
3000
2000
1000
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PEP-II Delivered Luminosity in 2003
PEP-II Total Delivered Luminosity for 2003
40000
35000
32.5 fb-1
30000
pb-1
25000
20000
15000
10000
Grand total delivered 135 fb-1
5000
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29-Jun
30-May
Time
30-Apr
31-Mar
1-Mar
30-Jan
31-Dec
0
11
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Near Term Luminosity Improvements to PEP-II
• New ring correction algorithms (MIA) –Now works
globally to fix beta beats and coupling. So far does not
work locally (IR). Next fix HER horizontal beta beats.
• New local by* knobs in HER and LER. Try for 9 mm.
• Increase number of bunches and currents. Need to watch
RF trips, vacuum heating, and backgrounds.
• Reduce HER emittance and raise LER emittance.
• Try continuous injection.
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Predicted Integrated Luminosity FY2003
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Overall plans to improve the PEP-II program
• Increase machine studies from 5% toward 15%.
• Restart the PEP-II Machine Advisory Committee with
the chairman David Rice (Cornell). (First meeting set
tentatively for October 9-11, 2003).
• Perform a Mid-Project Evaluation with PEP-II people
and outside-the-project people to refine our tasks.
• Welcome further participation of BaBar collaborators.
• Increase activities of the PEP-II RF Task Force.
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Luminosity Equation
 xy is the beam-beam parameter (~0.06)
• Ib is the bunch current (1 ma x 2 ma)
• n is the number of bunches (~942)
 by* is the IP vertical beta (~12 mm)
• E is the beam energy (3.1 and 9 GeV)
L  2.17x10
34
nx y EIb
b y*
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Overall goals for next year
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Raise HER beam current to 1.5 amps (now 1.1 amp).
Raise LER current to 2.7 amps (now 1.6 amps).
Increase number of bunches (942  1150).
Lower by* from 12  9 mm.
Raise the beam-beam parameter
– (move to nx=0.520.51).
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•
•
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Improve injection efficiency and rate.
Lower BaBar backgrounds.
Reduce component HOM heating.
Reduce the Electron Cloud Instability (ECI)
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Raise HER and LER currents
• HER has seven RF stations with six
in use. One missing a klystron. We
will add one more station this
summer.
• LER has 3 RF stations, all in use.
We will add a LER station in
Summer 2004.
• New low level RF controls and
feedback now coming on line.
• Still too many trips of RF stations.
Trip rate is the same as last year but
the beam currents are 15% higher.
• Two new klystrons and two repaired
klystrons should arrive in the next
six months.
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Increase the number of bunches
• The luminosity can be increased by
adding bunches.
• If the bunch charges remain the
same, the beam-beam effects are
unchanged and the luminosity
increases linearly with current.
• Higher current beams increase
heating issues in the vacuum
chambers.
• Increased currents mean that the RF
system must handle more current
loading but with added stability.
• The bunch-by-bunch feedback
systems also must work harder and
closer to specifications.
Luminosity along the train with By-3
bunch pattern and mini-gaps.
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Lower b y * in HER and LER
Nominal
With Hourglass
• Lowering b y * will increase
the luminosity. Try for 12 
9 mm.
• Must locally correct the
coupling and energy
dispersion in the IR after beta
reduction.
• Must reduce the bunch length
at the same time. We will
raise RF station voltages and
increase the number of RF
stations.
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Increase the beam-beam parameter
• We will increase the beam-beam
tune shift by moving to a better tune
location and by weakening beambeam resonances.
• Moving the horizontal tune closer to
the half integer allows the dynamic
beta effect to increase the tune shift.
• However, near the half integer betabeats from quadrupole errors are
worse and must be corrected.
• First MDs this week to move the
LER first has gone well. Will soon
move the HER to the half integer.
• The LER will be done first as the
HER is stronger in collisions.
LER tune plane vs. luminosity plot
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Octupole Magnets (from CERN)
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Lower BaBar backgrounds
• BaBar backgrounds are often good.
• Backgrounds can be poor during
injection (mostly HER) and at high
currents and luminosity.
• Muon IFR outer layers are often
swamped.
• A new HER upstream collimator
will be installed this summer. 
• In LER Pb shielding will be
installed upstream to reduce IFR
beam spray.
• Injection studies are being planned
to improve reliability.
HER horizontal collimator
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Old Longitudinal Kicker
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New Longitudinal Feedback Kicker Assembly
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New Longitudinal Feedback Kicker End Plug
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Transverse Feedback Kicker
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Reduce the Electron Cloud Instability (ECI)
Low energy electrons in the vacuum
chamber are attracted to the
positron beam and cause “head-tail”
instabilities. This is called ECI.
Solenoids have been shown to strongly
reduce this effect in PEP-II by
keeping the electrons near the
chamber walls. This summer we
plan to strengthen the solenoids in
the straight sections (x 3 in field) so
that bunches can be placed every 2
RF buckets (every 3 now). A
chamber distance of about 1 km is
to be wound.
ECI in the By-2 bunch pattern
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PEP-II Summer 2003 Projects
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New HER # 8 RF station (+200 mA).
New HER collimator (30 m upstream).
New Longitudinal feedback kickers.
Improved transverse feedback kickers.
Improved low level RF feedback circuits (higher I).
More x-y BPMs in IR2 region.
LER straight section and Arc 11 solenoid upgrade.
Octupoles for tune shift with amplitude studies.
Bellows fans on all LER bellows (~240)
Fix IR vacuum gate valves
Air cooling of Feedback Kicker cables
More background shielding of PEP-II in IR2
IR4 HOM damper
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FY2004 and longer plans
• Continue to increase luminosity each year  AIP funding
(Accelerator Improvement Projects)
• Big upgrade in the summer of FY 2005 by moving quadrupoles
closer the the interaction region and lowering by* to 6-7 mm.
• Continue to add RF stations (one station per year for five years)
• Some higher power vacuum chamber upgrades needed.
• Better beam controls needed: bunch-by-bunch feedbacks,
injection, backgrounds, Electron Cloud Instability,…
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PEP-II upgrade with Permanent Magnet Quadrupoles
Possible 2x1034 Interaction Region
with a ±3.25 mrad Xangle
30
QF2
QF5
QD4
20
Extra
focusing
QD1
QD1
QD1
QD1
Centimeters
10
9 GeV
0
-10
Extra
focusing
-20
QD4
QF5
QF2
-30
-7.5
-5
-2.5
0
Meters
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2.5
5
7.5
M. Sullivan
Jun. 14, 2000
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Path to higher PEP-II luminosity
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Luminosity
I+
IBeta y*
Beta x*
Bun. Length
# bunches
Vert. emit
Horiz. Emittance
Crossing angle
Beam-beam para.(x/y)
Number RF stations
Date hardware ready
Date for luminosity
5.2E33
1850
950
12
50
1.2
942
2.5
40/50
0
7.5/4.2
9
Nov 02
Mar 03
7.5E33
2400
1250
10
50
1.05
1180
1.4
35/45
0
7.5/4.4
10
Mar 03
Dec 03
1.5E34
3300
1600
8.0
50
0.9
1450
0.9
35/45
0
7.5/5.6
13
Nov 05
Fall 06
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2.5E34
4500
2000
6.5
50
0.8
1700
0.9
40/53
+/-4 (?)
8.2/5.8
15
Nov 07
Fall 08
Units
mA
mA
mm
cm
cm
nm
nm (+/-)
mrad
x100
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Long Range PEP-II Upgrades
• Over the next 4 years PEP-II will add:
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Four RF stations
Reduce by* from 12 mm to about 6.5 –7.5 mm
Somewhat better bunch-by-bunch feedbacks
Bellows cooling
Higher power vacuum chambers in the IR
Move quadrupoles closer to the IR but still permanent magnets
More and stronger sextupoles
More collimators
Better injection background hardware
More vacuum chamber solenoids
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PEP-II Summary
• PEP-II has delivered 33 fb-1 so far in Run 3 and a total of 135 fb-1
since May 1999.
• PEP-II is starting to take advantage of the FY2002 summer down
projects. There are several advances to go!
• Integrated luminosity is on the predicted track.
• Luminosity has increased to 6.485 x 1033 cm-2s-1. More machine
studies will help.
• Upgrades for Summer FY2003 are on track.
• There are long range plans leading towards L >2 x 1034 cm-2s-1.
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Comparison of KEKB and PEP-II to date
PEP-II
KEKB
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PEP-II and KEKB Possible Luminosity Gains
(estimated by J. Seeman June 2003)
Effect
PEP-II
PEP-II Gain
KEKB
KEKB Gain
Lower by*
12  7 mm
1.5
6  6 mm
1.0
Move x tune to 0.52
In progress
1.0
Done
1.0
Move x tune to 0.505
Later
1.2
In progress
1.1
Increase currents
In progress
2.0
In progress
1.3
Stronger LER solenoids
In progress
1.4
In progress
1.2
X-angle or Crab cavities
Not needed
1.0 (1.1)
2005-2006
1.5 (2.0)
Increased injection rate
30 60/120
1.1
Done (50 Hz)
1.0
Or Continuous injection
Needs study
1.1 (1.2)
Needs study
1.05
Or two bunch injection
Needs study
1.1
Done
1.0
Total factor
75% of gain
4.2 (5.0)
75% of gain
2.0 (2.7)
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K. Oide’s Prediction of KEKB’s Integrated Luminosity
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