Bylinsky, Yu V

Esin, S K

Fedotov, A P

Feshchenko, A V

Gorelov, D V

Korolev, O S

Mirzoian, A N

Murin, B P

Ostroumov, P N

Sharamentov, S I

Zharylkapov, S Zh

CERN Document Server

Particle Accelerators, 1990, Vol. 27, pp. 107-112Reprints available directly from the publisherPhotocopying permitted by license only© 1990 Gordon and Breach, Science Publishers, Inc.Printed in the United States of AmericaOPERATIONAL EXPERIENCE OF THE FIRST 20 MEV TANK OF THEINR LINACYU.V.BYLINSKY, S.K.ESIN, A.P.FEDOTOV, A.V.FESCHENKO,D.V.GORELOV, O.S.KOROLEV, A.N.MIRZOJAN, B.P.MURIN,P.N.OSTROUMOV, S.I.SHARAMENTOV, S.ZH.ZHARYLKAPOV.Institute for Nuclear Research of the Academy ofSciences of the USSR, Moscow 117312, USSR.Abstract Experiments with the proton beamacceleration in the first 20 MeV tank of the INR mesonfactory linac are presented. The detail investigationof the transverse beam parameters and longitudinalbunch shape are given.I NTRODUCTI ONThe H+, H- linac of the INR meson factory is under tuningnow. Recently the beam acceleration in the first 20 MeVAlvarez tank has been studied in detail 1. The preparationto accelerate the H+ beam up to 100 MeV is under way. Theresults of the beam parameter measurements are presented.The sketch of the main experimental equipment is shownin the Fi gure 1.BEAM~ S1\ FrrS':~tJBr f \\: PMI ! I \ I- '~- - 1tt1IHt-.tt-t-tt-tHHt-tr-tt++tt-if-~;~FIGURE 1 The layout of the experimental equipment.Legend: BM - bending magnet, BMS - emittancemonitor, Fe - Faraday cup, S -solenoid, B-buncher, WS -wire scanner, QD -quadrupoledoublet, Tl -tankK 1, eM -current monitor,BLM. ~bunch .length mon~dor, BP~ -bunchpOSItIon monItor, HRM -3 harmonIc cavitymonitor, VS -vertical slit, HS -horizontalsl i t.[353]/107108/(354] YD. V. BYLINSKY ET AL.The beam acceleration has been provided at 1 Hz repetitionrate but the tank has been driven at 10 Hz. Thelongitudinal and transverse beam parameters were comparedin the 10 Hz and 100 Hz rf operation mode in order toascertain a degree of the cavity heat loading influence onthe beam parameters. The change of the beam position andphase spectrum was insignificant.DETERMINATION OF RF AMPLITUDE AND INJECTION ENERGYTo determine an rf amplitude in the first tank we used bothtraditional amplitude scan method 2 and the method basedupon the phase spectrum measurements 3. The rf amplitudesetting results were discussed in ref 1.Typical experimental phase spectra of the acceleratedbeam for different rf amplitudes are given in Figure 2.1 ~ 0 ..96 Eo 0.98 Eo 1.00 Eo 1.02 Eo 1.04 Eoo>Q) 0-lw_o 15.J\--TT"" '~ITTrrlo 15 0 15 ({J d.ee,) ....~FIGURE 2 Typical phase spectra for different rfampl i tudes.The dependence of the phase spectrum maximum and bunchlength aF on E/E' are presented in Figure 3.AF.° Imrel.valuetZ10 -o f;t'0.97 0.98 0.99 1.00 t.Ot 1.02 t.03FIGURE 3 Phase spectrum maximum and bunch length asthe functions of the rf amplitude.OPERATION OF 20 MeV TANK [355]1109As the phase advance of the small longitudinal phaseoscillations does not depend on the injection energy, themethod of rf amplitude definition is not sensitive to ainjection energy error. The measurements made for twoenergies Wo and 0.99WO gave the same value of E'.The analysis of the experimental curves shows, thatthe accuracy of E' experimental determination is about 0,1%and the error of nominal rf amplitude determination is lessthen 0.2%. After the rf amplitude was precisely determined,the amplitude scan experiment was used to find nominalinjection energy more precisely. The nominal energy wastaken to satisfy a cutoff condition Ec=O.835EO.There is the two-cavity buncher at the entrance of thefirst tank. The setting of rf phase was carried outseparately for two cavities using the phase scan experimentwhile the first tank is excited to the nominal amplitude.BEAM PARAMETERS MEASUREMENT AT THE I NJECTI ON LI NEBeam emittance monitors of the slit-multiwire collectortype are used at the injection line. By using the resultsof emittance measurements the phase ellipse parameters arefound. The values of a, p, ~ and £ are used to calculatebeam optics and matching conditions between low energytransport line and the first tank acceptance. The resultsof emittance measurements are used to calculate thedependence of r.m.s. emittance on the beam currentfraction. The results of the multiple emittancemeasurements at the injection line are given in Figure4. The main purpose of the injection line is to match a beamemittance and the linac acceptance. The matching section ofthe injection line consist of three solenoids and onequadrupole doublet. The computer optimization providing4-dimensional matching (Without bunchers) is used to tunethe matching section. The experiments have shown that from10% up to 20% of the beam is lost at the matching section.The losses are caused by collimators placed at the entrance110/[356] YD. V. BYLINSKY ET AL.---- ------+-----t..-.,;...-~1fI_i~ J___----+----_4__---+----__+-~~1-1~J___--__+_---_4__---+__--__+~,_____;~_:_tI:1.•; ~_---+---~4----___4_:-=-~-~-i__:l:__---------~s:5c)(wiO-~LM...L.~....L....L..L~~~l_..L...L..~~~~.........................~.........~~..a..Jo 0,2. 0.4 0.6 0,8 t,O1/10 -----FIGURE 4 Horizontal plane emittance measurementresults at the two points along injectionline (BMSl and BMS2 are placed at 2.5m and7.5m after injector accordingly),I BMS1=150mA, I BMS2=110mA.of buncher cavities. This collimators are used to avoidcavity loading produced by secondary emission electronsoriginating due to beam losses. In spite of these lossesthe tuning of focusing channel provides ~100 rnA beamcurrent at the linac entrance. The reproduction ofoperation conditions enables to obtain 75'-100 rnA currentwithout additional tuning. Manual tuning was used to getmaximum current after any interruption of operation. Thefraction of accelerated particles was 29% for 95 rnA inputcurrent. The theoretical coefficient is 30% without spacecharge. It means that there are no losses because oftransverse motion in the first tank and the beam issufficiently matched to the linac. The matching proceduretakes into account variation of phase ellipse because ofspace charge effects. Six dimensional matching (bunchersturn on) theoretical condition was not succeeded to obtainbecause of focusing force limitations. Nevertheless thefraction of accelerated particles was 67% for single andOPERATION OF 20 MeV TANK [357]111180% for two operating buncher cavities accordingly. Thisvalues coincide with theoretical ones. The maximum value ofaccelerated current was 46 mAeACCELERATED BEAM PARAMETERS MEASUREMENTTwo methods were used to measure emittance at the tankexit. 1. Beam profiles for different gradients of thefocusing channel were measured. Variation of gradient leadsto changing of transverse oscillations phase advance. Inthis case the beam profiles represent different projectionsof a beam phase portrait. The results of profilemeasurements were used to calculate r.m.s. parameters ofthe beam emittance. Moreover the gradient variation leadsto the beam position changing, the value of changing beingequal to 4.5 mm in horizontal and 1 mm in vertical planes.2. Slit and wire collector was used. The plate withhorizontal and vertical slits was installed instead of thefirst wire scanner. The direction of the plate displacementwas 450 with respect to vertical and horizontal planes. Thesecond wire scanner was used as a beam collector (Figure1). The beam fraction vs normalized emittance is given inFigure 5.1.0,.J"_-;r7~ r.".E~~.~"" EyL .".~/~£/'I I I , l -. t , I I I I I I I0.51/10The dependence of the accelerated beamfraction on the normalized emittance value.10 -20.0FIGURE 5-0oLE*E 10-'o*~112/[358] YD. V. BYLINSKY ET AL.The value of effective emittance, containing N 100%particles, is limited by the acceptance of the first 22focusing periods (the aperture diameter equals to 15 mm).Inthe case of the maximum output/input current ratio (29%without bunchers) the accelerated beam emittance turned tobe the largest and was found equal to acceptance of thetank focusing channel. The experimental data show that thetotal emittance at the tank N 1 exit is 5-8 times smallerthan the acceptance of the next cavity focusing channel.The r.m.5. dimensions of the beam are 6-10 times smallerthen the channel aperture. The resolution of the bunchlength measurements was better than 1° (f=198.2 MHz). Thelength of the bunches depends upon the operation mode andwas varied from 20° up to 30°. Because of comparativelylarge values of dumping and phase advance of thelongitudinal oscillations the phase portrait is close tocanonical ellipse. Therefore the bunch length measurementscan be used to derive momentum spread. The 200-300 bunchlength corresponds to ~p/p= (1.0-1.5)%. At the exit of thetank K 1 unaccelerated particles are presented. Themeasurements of longitudinal density distribution insideand outside of the bunch showed that the number ofunaccelerated particles is less then 1% of the total outputcurrent.Authors are greatly indebted to operators andtechnical personnel of the various accelerator systems fortheir help during experimental shifts.REFERENCES1. Yu.V.Bylins~ et ale The 1989 Part. Accel. Conf.,(Chicago, March, 20-23, 1989).2. Jameson R.A. et ale LAMPF Report, LA-6863, (Los Alamos,1978) .3. Feschenko A.V., Ostroumov P.N. Proceedings of the 1986Linac Conf., (Stanford, June 2-6, 1986), p.323.

Operational Experience Of The First 20-mev Tank Of The Inr linac

Operational Experience Of The First 20-mev Tank Of The Inr linac

Abstract

Similar works

Full text

Available Versions

CERN Document Server