_#
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
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