brookhaven science associates rf systems for nsls-ii j. rose, a. blednykh, p. mortazavi and nathan...

BROOKHAVEN SCIENCE ASSOCIATES

RF systems for NSLS-IIJ. Rose, A. Blednykh, P. Mortazavi and Nathan Towne



Beam Energy 3 GeV

Beam Current 500 mA

Energy loss/turn (Initial/Upgrade)

0.9 /2.0 MeV

Power to Beam

(Initial/upgrade)

0.45 / 1 MW

p/p acceptance 3%

Momentum

compaction

0.00037

X-RAY Ring RF requirements

RF parameters

Frequency 500MHz

Cavity Voltage 3.3 / 4.9 MV Bucket for 3.3MV


NSLS-II RF POWER REQUIREMENTS

Covered in baseline cost

Capability of installed RF

Installing 3rd cavity+300kW

Adding 4th cavity and transmitter

Power # installed, power in kW

# installed, power in kW



Dipole -, 144 -, 144 -, 144 -, 144

Damping wiggler

3, 194 4, 259 8, 517 8, 517

Cryo-PMU 3, 38 6, 76 6, 76 10, 127

EPU 2, 33 4, 66 4, 66 5, 83

Additional devices

?, 200

TOTAL 409 545 803 1071

Available RF Power

540 540 810 1080


Cavity Choice

•High beam currents achieved by B-factories madeCESR-B, KEK-B and PEP-II cavities attractive

•Complex SUPERFISH analysis of CESR-B ofHOM impedances used in preliminary CBI growth rate estimates with ZAP: maximum growth time of 65ms for 4 cavities, less than the damping time of 8ms

•GdfidL analysis of full 3-D cavity extends analysis to dipole modes and 3-D effects (fluted beampipe)


Cavity Modeling with CFish, GdfidL

Alexei Blednykh

GdfidL vs. CFISHBenchmark ferrite losses, superconductor surface resistanceGdfidL vs. measurementson ferrite loaded pillbox confirm GdfidL modelFull Cavity HOM results used to analyze CB instability up to ~2GHz, No problems yet but need to extend to beampipe cutoff frequency of 7GHz


CESR-B Cavity chosen for Baseline

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 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)


KEK-B Cavity Parameters

Manufactured by Mitsubishi for KEK at 508 MHz They have produced one cavity at 500MHz

*KEK has recently demonstrated 400kW per couplerKEK cavity is an option for NSLS-II

*Shinji Mitsunobu SRF2005 ThP52 High Power Test of Input Couplers and HOM dampers for KEKB Superconducting Cavity

Frequency (MHz) 500

Energy gain/cav (MeV) 2.5

E-Acc (MV/m) >12

Unloaded Q @ 8MV/m >109

BeamPower/coupler (kW) >270


Passive Third Harmonic Landau Cavity

Elletra/SLS Super 3HC cryo-module

~1/3 of 500MHz voltage,~1 MV, can be met with one Super3HC cavity

A harmonic bunch-lengthening cavity is required to increase Touschek lifetime. Increases beam stability by increasing energy-dependent tune spread


1500MHz “Super-3HC” cavityVoltage/cell 0.5 MV

Eacc >5MV/m

Unloaded Q >7108

Static losses <50W

Dynamic + static losses

<100W

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)

N. Towne


NSLS-II RF Straight layoutTwo 500 MHz cavities + one 1500 MHz passiveharmonic cavity fit in one 8m straight: meetsinitial power requirements

Second straight reserved forthird , fourth 500 MHz and second 1500MHz cavities asadditional user insertion devicesincrease RF power requirement

Klystrons located in adjacent RF building to minimize loop delays in feedback systems


RF Power Sources for Ring System

Manufacturer/model Frequency

MHz

Power

kW

Efficiency

%

CPI VPK-7957A 500 800 60

Thales TH2161B/2178 500 310/800 61

Toshiba E3774 500 180 53

Klystron can be sourced by multiple vendors


Low Level RF System Amplitude modulation of the RF fields leads to momentum

deviations of the beam, Likewise phase modulations translate into amplitude modulations again leading to momentum deviations. The momentum errors affect beam size and orbit jitter as follows:The beam size in the center of the 5 m straight is given by

This work is in progress, and preliminary tolerances of +/- 0.5% amplitude

and 0.5 degree phase have been adopted. These values have been achieved at

other 3rd generation light sources.

22 , yyyyyxxxxx Since the dispersion is near zero (~1mm) and the natural energy spread is <0.001 the second term is negligible and the beam size becomes

σ x,y= 40μm, 2.4 μm

Effect of RFjitter on thebeam:

Orbit jitter is given as σx = σδ∙ηx , σy = σδ∙ηy σx′ = σδ∙ηx′ , σy′ = σδ∙ηy′


ε′

ε′′

μ′

μ′′

Modeling: Future work•NSLS-II bunch length of 4.5mm excites modes up to elliptical beam-pipe cutoff frequency•C48 Ferrite loss factor decreasing rapidly

Impedance limit for 8ms dampingtime, 4.5mm bunch length

Courtesy M. deJong, CLS

FI

VσR

os

rfradsh

rf

lim

Losses declining

By combining different ferrite tiles broad range of frequencies can be damped

V. Shemelin

0 40


Booster Ring Requirements

Full energy booster in same tunnel 780m circumferenceEnergy loss /turn =493 keV Vacc = 1MeV for 1% RF acceptance7nC/macropulse, 1 per min.Beam current = ~3mA Beam power 3kW

1 “Petra” type cavity and (1) 50-80 kW IOT Phase in 500 MHz (radians)D

elta

-E/E


Conclusions

RF systems for third generation light sources are mature technology; RF cavities and power sources available from industry

The short bunch length of 4.5mm in NSLS-II means operating the CESR-B cavities in a new regime, C-48 ferrite may not meet requirements at higher frequencies: This is being studied further, newferrite combinations appear to be direct substitutes and can be incorporated in the preliminary design phase.

Work continues to define RF tolerances, however modern digital RF control systems can achieve an order of magnitude improvement over existing (APS, ESRF) systems mitigating any concerns

brookhaven science associates rf systems for nsls-ii j. rose, a. blednykh, p. mortazavi and nathan...

Documents

d cavity

couplerkek cavity

passiveharmonic cavity

ghzcesrb cavity

rf power requirements

adjacent rf

rf systems

rf straight layouttwo