X-rayBoosterIRLinacHarmonic RF

RF Systems for NSLS-IIJ. Rose, A. Blednykh, N. Towne

With help from many others at BNL and other institutions

Beam Energy 3 GeV

Beam Current 500 mA

Energy loss/turn 2 MeV

p/p acceptance 3 %

Power to Beam 1 MW

X-RAY Ring RF requirements

0 1 2 3 4 5 62 10

8

1 108

0

1 108

2 108

Phase in 500 MHz (radians)

delta

E/E

Plot of 500 MHz stationary bucket and accelerating (radiation losses) bucket E=3 GeV, RF Cavity Voltage 4.9MV

RF parameters

Frequency 500MHz

Cavity Voltage 4.9 MV

Momentum

compaction

0.00035

Synchrotron

frequency

~35kHz

Baseline CESR-B Cavity

Beam energy gain/cav

>2.4 MV

Eacc >8 MV/m

Unloaded Q >7108

Standby (static) losses

<30 W

Dynamic + static losses

<120W

Operating Temperature

4.5 K

Max. beam power/cavity

<250 kW

Frequency 500 MHz

SCRF chosen for lower R/Q, highlydamped HOM’s, lower operatingcost and comparable capital cost

CESR-B has well established commercial production. Units 15 and 16 now being produced by ACCEL.In operations at Cornell (4), CLS(2), Taiwan (2). Being commissioned atDiamond (3). Ordered for ASP(?)

1500MHz “Bessy” cavity

Voltage/cavity 0.5 MV

Eacc >5MV/m

Unloaded Q >7108

Static losses <6W

Dynamic + static losses

<12W

Operating T. 4.5 K

Frequency 1500 MHz

Harmonic Cavity for Bunch Lengthening

4.9MV @500MHz required for 3%Momentum acceptance: 1.6MV @1500MHz requires 3 cavities

Work continues on effect of bunch traintransients on bunch lengthening

N. Towne

X-Ray Ring Layout• 4 - 500 MHz cavities (1MW req’d and 250kW/coupler)• 3- 1500 MHz cavities (4.5MV @500MHz=1.5MV At 1500MHz and 0.5MV/cav)

Stray magnetic fields at cavities must be << 0.5 Gauss at cooldown !

IR Ring RequirementsVacc >2.5MV Beam current =1.0A (1.5)Beam power <10 kW

1 SCRF module(1M$ cavity, 0.2M$ RF + >120W @4.5k cryoplant)

Low beam power means either matching stubs or adjustable coupling Benefits from Antennae Coupler !

Fwd. and Rev. Power vs. I

•Thales 310kW transmittercosted, one per cavity@ 2.3M$ ea

•CPI 800 kW klystron existsif dual or high power coupleradopted (can be optimized for 600kW)• Option: Combine 50 kW IOT’s from broadcast industry (times 6 or 12 does not seem attractive,will study Diamond’s results)•Will use IOT’s for Booster, IR ring

RF Power Source Options

TH2161B installed at CLS

Booster Ring RequirementsEnergy loss per turn = 1MeV, Vacc = 2MeV for 0.9% RF acceptanceNegligible Energy gain per turn ~29 keV for 300ms rampBeam current = ~3mA (~6mA for IR) Beam power 3-6 kW

2 “Petra” type cavities and 2 -50kW IOT’s(1.5M$ cavities + 0.4M$ RF)

OR 1 SCRF module + 1 -50kW IOT (1M$ cavity, 0.2M$ RF + >92W @4.5k cryoplant)

Cavity Modeling with GdFdl

GdfidL vs. CFISHBenchmark ferrite losses, superconductor surface resistanceGdfidL vs. measurementsConfirm ferrite properties

Full Cavity results are nowbeing calculated to be used to analyze CB instabilityNext is coupler analysis,Cavity pair with spool piece

Alexei Blednykh

MOTIVATIONReduces # X-ray cavities from 4 >2which reduces ring impedanceAdjustable coupling to minimize IR ring, Booster rf power req’d.Lower static cryo-losses Frees up 6m straight !

R&D roadmap for power coupler

R&D needs:•RF transmitter•Coupler development•Coupler test stand •Cryo-test facility•Cavity prototype

FOR NSLS-II: Dual antennae coupler design most appealing !•250kW/coupler has been demonstrated, 500kW/cavity low technical risk.•Adjustable coupling allows better matching for low power requirements of Booster, IR rings: need only one coupler: lower cost

•Road to upgrade: Add HOM to IR ring 2nd coupler port?

Cryo-Plant RequirementsX-ray -4.9MV 4 Cavities 2 cavities

Cavity V 1.23 MV 2.45 MV

Static load 30W ea 30W ea

Dynamic load 26 W ea 98 W ea

Valve box ~30W* total ~30W * total

Harmonic cav. 3 @ 15 W 3@15 W

+1W/m transfer lines

100 W * 75 W*

IR Ring (30Static +98Dynm.+30VB) W

Booster (30Static +62Dynm.+30VB) W

Total 679 W @ 4.5K 686 W @ 4.5K* Not sure how many VB’s needed, how many meters of transfer line

• Frequency 2.9983 GHz

• Length 5.2 m

• Shunt imp. 51 M/m

• Q 14000

• Filling time 0.74 s

• Energy gain 12.6*sqrt(PMW )

• Attenuation = 0.55 Np

2.998 GHz LinacPicture courtesy of ACCEL

Energy gain 80MeV/tank for 40MW power input (no-load)

1 Klystron TH2100 (45MW) per accelerating tank

Solid state modulator to drive klystron

Low Level RF•Emphasis to date has been on cavity choices and high power systems which have immediate impact onbeam dynamics, ring layout, and have longer lead times.

•Unlike the cavities and high power systems the LLRF is likely to be upgraded throughout the life of the project.

•Take advantage of the flexibilty of new digital RF systems and direct IQ modulation at 500 and 2998MHz.

•Unlike the high power systems LLRF is not available commercially, and skills need to be in-house. Digital RF requires additional skill set (e.g., the rf programmer)

Conclusions•RF requirements for NSLS-II can be met with existingtechnology, often from commercial sources

•Development of high power and/or dual antennae couplerwould reduce number of cavities from 4 to 2 in X-ray ring, reducing impedance, freeing up ID straight. Allows more efficient low power operation in Booster, IR rings. Upgradeable, not locked in to existing performance.

•Need to continue work on cavity modeling and impedance calculations, analysis of bunch lengthening with harmonicRF in the near term, and later on systems analysis and LLRF