accelerator summary 1/22/2004 k. oide (kek). accelerator session: pep-ii ir upgrade m. sullivan...

Accelerator Summary

1/22/2004K. Oide (KEK)

Accelerator Session:PEP-II IR Upgrade M. Sullivan (SLAC)Super KEKB Optics & IR Y. Ohnishi(KEK)Super-PEP-II IR Upgrade M. Sullivan (SLAC)HOM calculations of new RF cavities A. Novokhatski (SLAC)RF system for Super-KEKB K. Akai (KEK)RF and longitudinal stability in Super-PEPII D. Teytelman (SLAC)

Accelerator Discussion and Contingency:Coherent Synch. Rad. Y. Ohnishi(KEK)Luminosity of Super KEKB J. Flanagan(KEK)

L 2ere

Iy

y*

z y*

Head-on collision:◆Parasitic crossing for large number of bunches◆Background due to separation bends

Crossing angle: ◆degrades y, < 0.06

◆restored by crab crossing

Smaller y*:◆Smaller physical/dynamic aperture◆Shorter lifetime, more background, …

Shorter z:◆More HOM heating◆ Coherent synch. rad.◆Shorter lifetime, more background

Higher Current:◆More rf power, cooling, injector, …◆More HOM heating (more bunches)◆Beam Instabilities◆Electron clouds, fast ions, …

Upgrade Scenario

L

2ere

Iy

y*RLRy

L (/nb/s) ILER (A)y*

(mm)y

P (MW)

Present Performance

PEP-II 7 1.8 12 0.05 ~50 Head-onKEKB 11 1.6 6 0.05 ~50 ±11 mrad

Upgrade before 2007 (without major funding issues)

PEP-II 33 4.56

z?0.05 ~60?

Head-on or small

crossing angle?

KEKB 30 1.6 6 0.14 ~50 crab crossingMajor Upgrade

PEP-II 1000 231.5

HOM? CSR?

0.10 ~150High freq rf,New tunnel?

KEKB 250 9.4 3 0.14 ~90 New beam pipe, more rf

PEP-II Proposed Upgrade Plans

Now Projected UpgradeLER energy 3.1 3.1 3.1 GeVHER energy 9.0 9.0 9.0 GeVLER current 1.8 3.6 4.5 AHER current 1.0 1.8 2.0 A

y* 12.5 8.5 6 mm

x* 28 28 28 cm

X emittance 50 40 40 nm-radEstimated y

* 4.9 3.6 2.7 m

Bunch spacing 1.89 1.26 1.26 mNumber of bunches 1034 1500 1700Collision angle head-on head-on head-on mradsBeam pipe radius 2.5 2.5 2.5 cm

Luminosity 6.61033 1.81034 3.31034 cm sec

M. Sullivan-1

0

0.1

0.2

0.3

0.4

0.5

0.6

0 2 4 6 8 10 12

LER First PC y,

l = 9 mm

by*=0.9 cmby*=0.8 cmby*=0.7 cmby*=0.6 cmby*=0.5 cm

2PC/I P

/2 (mrad)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 2 4 6 8 10 12

LER First PC y,

l = 7 mm

by*=0.9 cmby*=0.8 cmby*=0.7 cmby*=0.6 cmby*=0.5 cm

2PC/I P

/2 (mrad)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 2 4 6 8 10 12

HER First PC y,

l = 9 mm

by*=0.9 cmby*=0.8 cmby*=0.7 cmby*=0.6 cmby*=0.5 cm

2PC/I P

/2 (mrad)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 2 4 6 8 10 12

HER First PC y,

l = 7 mm

by*=0.9 cmby*=0.8 cmby*=0.7 cmby*=0.6 cmby*=0.5 cm

2PC/I P

/2 (mrad)

LER PC tune shifts vs /2 for different y* normalized to

the IP tune shift for l (bunch length) = 9 and 7 mm

HER PC tune shifts vs /2 for different y* normalized to the

IP tune shift for l = 9 and 7 mm

The tune shift from the first parasitic crossing normalized to the main collision tune shift as a function of crossing angle and plotted for various y

* values for PEP-II (courtesy of Marica Biagini)

M. Sullivan-1

M. Sullivan-1

The initial upgrade proposal replaced the last 4 slices of the B1 magnets with quadrupole field. This allows for lower beta y* values with a smaller increase in the maximum beta y.

The replacement of the B1 slices with quad field introduces a ± 3.3 mrad crossing angle at the IP which reduces the beam-beam effect at the 1st parasitic crossing. However, recent beam-beam simulations indicate a luminosity reduction for beams with a crossing angle.

An alternative proposal currently under study is to strengthen the IP end of QD1 effectively moving the center of the magnet closer to the IP. At the same time, increase the beam separation at the 1st parasitic crossing by increasing the strength of the initial B1 slices. This maintains the PEP-II head-on collision.

The high beam currents of the upgrade plans generate significant SR power in the IR that must be handled

SR backgrounds look like they can be controlled but have not yet been thoroughly studied

Summary M. Sullivan-1

QC2LP

QC2RPQCSL QCSRQC1LE

QC2LE

QC1RE

QC2RE

← LER

HER →

IP s (m)

x (m)Super KEKB IR magnet layout

Y. Ohnishi

QCS for SuperKEKB and KEKB

Move QCS closer to IP and compensation solenoid isdivided into two parts, one is overlaid with QCS.

SuperKEKB

KEKB

=17°=150°

EFC

Y. Ohnishi

QC1(superconducting magnet)

G=42.86 T/mLeff=0.232 mIop=1319A, Bmax=1.62 TIop/Ic=59%

QC1LE

Leakage field<1.5 Gauss

QC1RE

Leakage field<20 Gauss

G=34 T/mLeff=0.266 mIop=1319 A, Bmax=3.28 TIop/Ic=73%

Y. Ohnishi

Injector linac for SuperKEKB

1. Positron dumping ring (1 GeV)2. Positron energy upgrade with C-band

for energy exchange (e- LER / e+ HER)

Y. Ohnishi

Dynamic aperture

Injectionbeam

Coupling Lifetime

1% 51 min

2% 72 min

4% 102 min

6% 145 min

Dynamic aperture in LER Machine errors are not included. Transverse aperture is acceptable.

Y. Ohnishi

• Strategy of IR design• Positron DR prior to IR upgrade• Design of IR magnets• Two options for QC1 :

– superconducting / normal • IR magnets is designed so that SR from QCS does not hit QC1 and QC

2 as possible.• Vacuum chamber in IR is under study.• Optics for SuperKEKB is designed.

– Dynamic aperture in LER ( p/p0 ~ 1.5 %)– Injection aperture can be kept.

Y. OhnishiSummary

PEP-III Super B

Now Projected Upgrade Super BLER energy 3.1 3.1 3.1? 3.5 GeVHER energy 9.0 9.0 9.0? 8.0 GeVLER current 1.8 3.6 4.5 22.2 AHER current 1.0 1.8 2.0 9.7 A

y* 12.5 8.5 6.5 1.5 mm

x* 28 28 28 15 cm

X emittance 50 40 40 70 nm-radEstimated y

* 4.9 3.6 2.7 1.7 m

Bunch spacing 1.89 ~1.5 1.26 0.63 mNumber of bunches 1034 1500 1700 3400Collision angle head-on head-on 03.25 12-14 mradsBeam pipe radius 2.5 2.5 2.5 1.5-2.0? cm

Luminosity 6.61033 1.81034 3.31034 11036 cm sec

M. Sullivan-2

0

10

20

30

-10

-20

-300-5 5m

cm

Super B-factory IR

E36_2_5M_8_RL

M. Sullivan, Jan. 16, 2004

QD1QD1

QF2

QF2

QD4

QF5

QD4

QF5

HER

LER

83 kW

11 kW

40 kW

200 kW

M. Sullivan-2

0 0.5 1-0.5-1

0

2

4

-2

-4

cm

m

Super B-factory +/- 14 mrad crossing angle

HER

LER

from: B3$E36_2_5M_8_R,L.OUT

M. Sullivan, Jan. 16, 2004

A 1 cm radius beam pipe might be possible now

M. Sullivan-2

A super B-factory IR is quite challenging

The very high beam currents rule out designs in which SR fans are intercepted locally

The IR design in the areas of detector backgrounds, HOM power and SR quadrupole radiation are all very difficult and need to be thoroughly studied.

The trick is to find a solution that satisfies all of these requirements without compromising the physics

Summary M. Sullivan-2

Electric force lines of wake field excited by a short bunch in PEP-II cavity

A. Novokhatski

Spectrum of 952 MHz cavity

Loss impedance of this cavity is 3.4 times smaller than impedance of PEP-II cavity for a bunch of 1.8mm length. R/Q of the cavity is 66 Ohms

A. Novokhatski

Optimization of the cavity shape

Gives better R/Q =78 Ohm and less loss impedance by 8%

A. Novokhatski

Minimum loss impedance and loss impedances of different cavities

A. Novokhatski

HOM Power Loss in the Super B-factory Cavity f=136kHz h=3492

Cavity Frequency Pipe R/Q Bunch Total Above Beam Bunch Wake HOM type radius length Loss cut-off current charge Voltage Power

[MHz] [mm] [Ohm] [mm] [V/pC] [V/pC] [A] [nC] [kV] [kw]

PEP-II 476 47.6 114 13 0.4699 0.0849 2 11.14 0.95 1.89CESR-III 500 120 46.2 10 0.175 0.1014 2 11.14 1.13 2.26

PEP-II 476 47.6 116 4 0.805 0.389 11 23.44 9.12 100.32CESR-III 500 120 46.2 4 0.291 0.2174 11 23.44 5.10 56.06

KEKB-SC 508 110 44.9 4 1.326 1.192 11 23.44 27.95 307.40with tapers 75KEKB-SC-NT 508 110 47.7 4 0.318 0.2373 11 23.44 5.56 61.20no tapersPEP-II-Large 476 95.25 74.9 4 0.35 0.209 11 23.44 4.90 53.90

PEP-II 476 47.6 116 1.8 1.217 0.794 15.5 33.03 26.23 406.56CESR-III 500 120 46.2 1.8 0.448 0.3744 15.5 33.03 12.37 191.71KEKB-SC-NT 508 110 47.7 1.8 0.498 0.4173 15.5 33.03 13.79 213.68

PEP-II-Large 476 95.25 74.3 1.8 0.538 0.397 15.5 33.03 13.11 203.28PEP-II-Large 476 95.25 74.3 1.8 0.538 0.397 23 49.02 19.46 447.60

New PEP-II 952 47.6 66.4 1.8 0.748 0.472 15.5 16.52 7.80 120.84New PEP-II 952 47.6 66.4 1.8 0.748 0.472 23 24.51 11.57 266.08

PEP-Ellips 952 47.6 75.8 1.8 0.719 0.434 23 24.51 10.64 244.66

PEP-SC 952 77.62 31.6 1.8 0.303 0.208 23 24.51 5.10 117.25

A. Novokhatski

Summary

• To be continued!

A. Novokhatski

RF parameters for SuperKEKBRing LER HERBeam current (A) 9.4 4.1Wiggler magnets yes (half) noEnergy loss/turn (MeV) 1.2 3.5Loss factor, estimated (V/pC) 40 50Radiation loss power (MW) 11.3 14.3Parasitic loss power (MW) 7.1 1.7Total beam power (MW) 18.4 16.0Total RF voltage (MV) 14 23

(Total)Cavity type ARES ARES SCC ARES / SCCNo. of cavities 28 16 12 44 / 12Voltage /cav. (MV) 0.5 0.5 1.3Loaded-Q value (x10E4) 2.4 2.4 4.0Beam power /cav. (kW) 650 650 460Wall loss /cav. (kW) 233 233 -Detuning frequency (kHz) 45 20 74

Klystron power (kW) 930 930 480No. of klystrons 28 16 12 56Total AC plug power (MW) 42 24 10 76

K. Akai

Modification of LER-ARES• The ARES in LER will be remode

led to increase the stored energy further.

• By enlarging the coupling hole between the A-C cavities, Us/Ua will be increased from 9 to 15.

• Storage cavity is reused.

exsisting

modified

Energy ratio 1:9 1:15

Detuning (kHz) 65 45

Growth time (ms) 0.3 1.6

C-damper (kW) 41 26

100

101

102

103

104

9 12 15 18

Us/Ua

=−

=−

=−3

Coupling impedance for the p/2 mode

Growth rate as a function of Us/Ua

T. Kageyama, et. al.

K. Akai

Improve the ARES-HOM dampers• The waveguide dampers

– High power tested up to 3.3 kW/bullet (26 kW/cavity).

– Upgrade needed to 80 kW/cavity.– Will be tested at higher power with a new high power

source.– The number of bullets/waveguide will be increased.

• The grooved beam pipe dampers– High power tested up to 0.5 kW/groove (2 kW/cavit

y).– Upgrade needed to 20 kW/cavity.– A new type of damper? Such as a winged chamber wi

th SiC bullets?

Y. Suetsugu, et. al.

K. Akai

Beam pipe diameter 150 mm (present) 220 mm (enlarged)

Loss factor for 3mm bunch

2.46 V/pC 1.69 V/pC

HOM power for 4.1A, 5000 bunches

83 kW/cavity 57 kW/cavity

Influence to other groups

No change Replace chambers

Large bore magnets

Develop gate valves

SCC HOM power and beam pipe• Present HOM dampers in KEKB have been operated up to

12 kW/cavity.K. Akai

Schematic drawing of new crab cavity

• (Left) The cross-shaped waveguide dampers and coaxial dampers are attached at the squashed-cell.

• (Right) Cross section of the coaxial damper at the cut plane of Y-Y’.

coaxial damper

cross-shapedwaveguide dampers

Y

Y'

absorber

(cross section at Y-Y')K. Akai

Summary of SuperKEKB RF system

• Base plan:– The existing RF system will be used as much as possible, with improvements as ne

cessary. – The ARES (LER, HER) and SCC (HER) will be used.

• CBI due to the accelerating mode– LER-ARES will be modified, that eases the growth time from 0.3ms to 1.6ms.– The -1 mode damper will suppress the CBI with a growth time of 1 ms.

• HOM dampers– Performance limit of the present HOM dampers will be tested.– A new HOM damper may by necessary, particularly for the GBP damper.

• Large RF power– Improvement of the couplers will continue to double the operating power.– The number of RF unit will be doubled.

• Crab cavity– A new crab cavity is proposed, which can be used at 10 A. – The design is completed. It has sufficient property for SuperKEKB.

K. Akai

D. Teytelman

D. Teytelman

D. Teytelman

D. Teytelman

D. Teytelman

D. Teytelman

D. Teytelman

D. Teytelman

D. Teytelman

D. Teytelman

Coherent Synchrotron RadiationEnergy change / particle v.s z/z

KEKB LER/ 2.6A (5120)

Numerical simulation with mesh (Ago and Yokoya, to be published or details found in LoI)

Y.Ohnishi

Acceleration

Deceleration

E ≈ 100 kV/turn (5 V/pC) for 9.4 A, LER

Stubility must be checked