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WIDE

Y. Irie#, SD. Ho

M

Abstract A low-out

harmonic ferbeen developNational LabAppleton Ladriver stage 240kW triodoutput impedrange of 2.6waveform inissue. It was arranging thehave differen

Precise phthe fundamemotion and low output-ifrom heavy b

___________________________#yoshiro.irie@kek

EBAND L

. Fukumotooran, R. Kuathieson, A

tput-impedancrrite-loaded caped by collaboratory (US)aboratory (Uwith 250kW

de, both of whdance is less 6-6.2MHz. Hn the driver st

found such de two anode nt higher-orde

INTROhase control oental one is eto maximize impedance RFbeam loading,

_________________

k.jp

LOW-OUSEC

o, K. Muto, ustom, M. M. Seville, J.

ce RF systemavity in the ISaboration [1] ), KEK (Japa

UK). The sysW tetrode and hich are operatthan 30 Ω ov

However, distotage have bee

distortions couchokes of ther-mode charac

ODUCTIONf the second hessential to sthe stable ph

F system (LO, has been inve

Figure 1: S

UTPUT IMCOND H

H. NakanisMiddendorf (

Thomason

m for the secIS synchrotrobetween Arg

an) and Ruthestem comprisa final stage ted in class A

ver wide frequortions of voen a long-stanuld be mitigatee vacuum tubcteristics.

N harmonic cavstabilize the hase space areOI), which isestigated for f

Schematic of

MPEDANHARMON

hi, T. Oki, A(ANL, Argo(STFC/RA

cond-on has gonne erford ses a

with A. The uency oltage nding ed by

bes to

vity to beam ea. A s free future

highcharagrid overΩ, anFig.1[2], discu

Alvoltavoltadistotunintunewave

HI

Aselem

the low outpu

NCE RF SYNIC CAVI

A. Takagi (Konne, U.S.A

AL/ISIS, Chi

h-intensity acteristics areof the final t

r the wide frend the voltage1 shows the sccomparisons ussed in detaillthough the cage waveformage) was distoortions bring sng loop, and m. In the followeform distorti

IGHER-OR

s is well knments of induc

ut-impedance R

YSTEM FITY

KEK, IbarakA.), D. Baylilton, Didco

synchrotrons.e realized by triode amplifiquency rangee gain of the fchematic of thof measurem

l. cavity voltagem in the driorted, especiaserious phase make it difficuwing sectionson are discuss

RDER-MOCHOK

nown, an elctor, capacito

RF system.

FOR THE

ki, Japan), Jley, I. Gardnot, Oxon,U.K

The loa feedback f

fier. The outpue of interest isfinal triode is mhe LOI system

ments with cal

e showed a siver stage (h

ally above 5Merrors into th

ult to operate s, measures tosed.

ODE OF ANKE ectric circuit

or and resisto

E ISIS

J. Dooling, ner, R. K.)

ow-impedancefrom plate tout impedances less than 30more than 20.

m. In referencelculations are

ine-wave, theereafter, grid

MHz [3]. Suchhe ferrite biasthe cavity on

o mitigate the

N ANODE

t with manyor is liable to

e o e 0 . e e

e d h s n e

y o

Proceedings of IPAC’10, Kyoto, Japan MOPEC063

04 Hadron Accelerators

A15 High Intensity Accelerators 609

have a comparallel andexample, is capacitance bimpedance fundamental (HOMs) are is driven in a6.2MHz. The

(v t

where ω0=23.6×10^4. Si≤6.2MHz, anrange exist system, howshould also vacuum tubecomponents resonances waveform wi

The circuithe LOI anamodelled byexpressed byto couple thK=0.5, and adjacent one assumed for their distancresistor, 20k,simulation, nto be 13 for between platimpedance isresonant freqand the 1st H

Figure 2: Imand N2=0 (r

mplicated impd series reso

never of pubetween eachof the LOmode (3.9M

seen. As is ina frequency swe driver input

(

() 0

∑∞

−∞=

∝

∝

nn mJ

tSint ω

2π×4.4MHz, ince Jn(m) is ny frequency at anytime in

wever, higher hexist due t

e. It can be thhave a chancwhich exist ill then be disit simulation alysis. In the

y the circuit iy an inductanche adjacent cothe next adjaby 0.1. Similthe coil pairs

ce as 20pf, 1, is attached anumber of termthe anode chote and grid ofs also shown

quencies of theOM ( ~11.3M

CIRCUIT

mpedance of thright). N1 and

pedance struonances. A rure inductanc

h coil elementOI anode chMHz) and hn the ISIS synwept mode atis then written

()

(

0 −

Ω+

nSinm

tSinmt

ω

Ω =2π×50Hznon-zero on

components on the RF cyharmonics of to non-linearhought that ace to grow by

in the systtorted by thescode, TopSpie simulation, in Fig. 3. Eacce L1, L2, etcoil by the coacent one by larly, capacitivs to be inverse0pF, 20/3pF across each cominals is chookes and 5 forf the final trio

in Fig. 2 fore fundamenta

MHz) agree we

SIMULAT

he driver anodN2 stand for

ucture with mreal inductorce, but has t. Fig. 2 showhoke, wherehigher-order-mnchrotron, thet 50Hz from 2n as,

,)

))

Ω tn

t

z and m=Δωly for 2.6≤ ωover the frequ

ycle. In the af these compor response ofall these frequy exciting reltem. The orise spurious moce [4], is use

an inductorch coil eleme

c which is assuoupling coeffi

0.3 and the ve coupling isely proportionand so on. Soil element. Isen, for simplr the feedback

ode. The calcur comparisonl mode (~3.8M

ell with each o

TION

de choke withtotal turns and

many r, for stray

ws an the

modes e LOI 2.6 to

ω/Ω= ω0-nΩ uency actual onents f the uency evant iginal odes. ed for r was ent is umed

ficient third

s also nal to Shunt In the licity, k coil ulated . The MHz) other.

GrplateparamLOI,withcaviti.e. LcapachosTopSdistofeatuexpebecoand whenfor dcoil wexpeimprfrequfew locatwereterm

Thdissivacuacce

h N1=36 and Nd shorted turn

F

rid-to-cathodee-to-grid impemeters to cha, these param

h measurementy (Lcav) was sLcav(t)=1/(ω2(

acitance, 1,76sen to be 53Spice has notortions in thures under slierimental onesomes smaller

(2) such divn the 1st HOMdriver and finawas treated as

eriments werrovement in uency of the1turns at one

tions are diffe damped by

mination resisto

EXPEhe LOI is opeipations, a griuum tubes: gleration cycle

N2=5 (middlens at one end, r

Figure 3: Indu

e impedance (edance (Zpg) aaracterize the

meters were cnts. The inducso changed tht) Ccav), whe0pF. The cav38ohms [3]. t been able to

he experimenghtly differens: (1) system value, i.e. w

vergence/ disM peaks locaal anode choks a simple coilre performed

the followist HOM peakend of the a

ferent with eay adding a sor R~280ohm

ERIMENTAerated in classid switching sgrid bias is e, and at cutoff

e), and its simurespectively.

ctor model wi

(Zgk) in the driat the triode LOI [5]. In

confirmed to ctance of the hat the cavity sere Ccav is thvity shunt im

Although sio reproduce t

nts, it showent conditions

diverges fastwith lower cav

tortions can ate at differenkes. Althoughl in the latter cd aiming foing two cask was shifted anode choke ach other. Caecondary wins to the anode

AL RESULs A. In order scheme is appset at conduf in another ha

ulation model

ith 5 terminals

iver stage andare importantmodeling thebe consistentferrite-loadedstays on tune,

he cavity gapmpedance was

imulation bythe waveformed interestingfrom the realter when Ccavvity Q-value,be mitigated

nt frequenciesh the feedbackcase, or waveformses. Case 1:by shorting aso that peak

ase 2: HOMsnding with ae choke.

LTS to save plate

plied for bothuction in thealf-cycle.

l with N1=12

s (4 turns).

d t e t d ,

p s y

m g l v ,

d s k

m : a k s a

e h e

MOPEC063 Proceedings of IPAC’10, Kyoto, Japan

610

04 Hadron Accelerators

A15 High Intensity Accelerators

Closed loop controls for cavity tuning and RF voltage level were not implemented yet in this experiment. However, the ferrite-bias current was controlled manually so as to minimize the cavity input current. Experimental conditions are summarized in Table 1. In the anode chokes, N2 turns were shorted to shift the 1st HOM peak toward higher frequency as shown in Table 2. The frequency difference between the driver and anode chokes is then 1.695MHz instead of 1.183MHz. Detailed waveforms are compared in Figs. 4 and 5 on the effect of peak shift. Grid voltage waveform is greatly improved above 5MHz.

Experiment was also performed for the anode chokes with a damping resistor. The results were, however, very similar to those in Fig. 5.

Table 2: 1st HOM Location of Anode Choke [MHz]

Driver anode choke (N1=36) Final anode choke (N1=46) N2= 0 N2= 4 N2= 0 N2= 7 9.338 10.803 10.521 12.498

CONCLUSIONS A wideband low-output impedance RF system has been

developed in collaboration with the labs, ANL, RAL and KEK for the future high-intensity proton synchrotron. The system operates in class A, and output impedance is less than 30ohms over the frequency range 2.6-6.2MHz at 50Hz repetition rate. By modifying the anode choke characteristics, a long-standing issue on the waveform distortion at the grid voltage was improved significantly, although there still exists a distortion to some extent above 5MHz. Further investigation for improvement is

required for the beam test in the ISIS synchrotron, which is planned in February, 2011.

Table 1: Parameters of LOI Operation repetition rate 50Hz class of operations class A for triode and tetrode duty factor 54% by grid switching RF frequency 2.6 MHz (t=0msec)

~ 6.2 MHz (t=10msec) RF OFF RF ON Triode Supply: anode voltage average anode current grid voltage at conduction grid voltage at cutoff

16.6kV 12.1A

15.2kV 14.2A -340V -500V

Tetrode Supply: anode voltage average anode current G1 voltage at conduction G1 voltage at cutoff G2 screen grid voltage

6.6 ~ 6.7kV 14 ~ 17A 1.4kV

6.6 ~ 6.7kV 13 ~ 16.2A -60V -200V 1.4kV

ENI A-300 output 25Vrms

REFERENCES [1] http://www-accps.kek.jp/Low-Impedance_Cavity/ [2] T. Oki et al, EPAC’04, Lucerne, July 2004,

TUPKF034, p.1036 (2004); http://www.JACoW.org. [3] Y. Irie et al, EPAC’06, Edinburgh, June 2006,

MOPCH118, p.321 (2006); http://www.JACoW.org. [4] Penzar Development, P.O.Box 10358, Canoga Park,

CA91309 USA [5] T. Oki et al, Nucl. Instr. and Meth. A565 (2006) 358.

2.70MHz 4.04MHz 5.04MHz 6.25MHz

Figure 4: RF waveforms without HOM peak shift (N2=0). From top trace, grid voltage (143×), cavity gap voltage (1,590×) and cavity input current (20A/V) .

2.70MHz 4.07MHz 5.17MHz 6.24MHz

Figure 5: RF waveforms with HOM peak shift (N2≠0). From top trace, cavity gap voltage (1,590×), cavity input current (20A/1V), grid voltage (143×) and grid input current (20A/1V).

Proceedings of IPAC’10, Kyoto, Japan MOPEC063

04 Hadron Accelerators

A15 High Intensity Accelerators 611