Comrrtissioning Status of Indus-1 SR Facility G Singh *

Indian Journal or Pu re & Applied Ph ysi cs Vol. :19. January-Fehruary :WO I . pp. 1!6- 10:1

Comrrtissioning status of Indus-1 SR facility G Singh *. D Angai -ICdinin. D D Bhawalkar, A A Fakhri, AD Ghoclke. Pracleep Kant , Pracleep Kum ar. P K Nema. AS Raja Rao . G K Sahon & B Singh

Accel erator Programme. Cen tre for Advanced Tec hn ology. Indore 452 0 I :1

Received 7 Novernher. 2000

The Indu s- I sy nchrotron ra diatiun fa cility consist s or synchrotron. storage ring. Maximum current oi' I (, I mA was acc umulated in th e Indu s- I storage ring. Beam dynamics studi es carried out on these machines during th e commissioning

Introduction of th e parameters of th e injec tor syste m are give n tn Table I . lnclu s- 1 is a 450 M eV st ora ge ring which will mainly provide th e radiati on in th e VUV region or Tahle- 1 - Parameters or injector sy.;tem 1 2 S ynch rot ron the electromagneti c spectrum . The sy nchrotron is used as an injec tor, which i.· ca pable of increas ing Maximum energy 700 M eV ':' th e energy or 20 M eV elec trons as injec ted from a Current 30 mA':":' cla ssica l microtron to 450 M eV for injec ti on into Circumference 2X.45 111 lndus- 1. The la yout or lnd us- 1 fa cility is shown in Bending rad ius I.X 111 Super-peri ods (, Fig. I. The microlron. transfer lines and synchrotron RF frequ ency 3 1.61 3 MHz ha ve alread y bee n commissionecl q The lnclus- 1 Repetition raiL' 1-2 Hz stora ge ring was commissioned in 1999. Two Harmonic number 3 ex tracted bunches out or three bunches from th e Microtron sy nchrotron arc injec ted inlo th e stora ge ring using a single ki cker. The set tings or th e injec ti on septum, 13 eam energy 20 M eV k ickcr. d i pok s, quadrupoles ha ve bee n optimised Pul se current 25 1ni\ and a stored current or 161 mA was achieved in Pul se dur;llion I ps .Jul y 1999. The beam lifetime at the design current Accelerating frequency 2X56 M 1-11. Repetition rate 1-2 Hz of I 00 mA is presently limi ted due to th e vacuum. * Presen t operat ing energy. 450 M t' V Res ults or th e initial commiss ioning ex periments ** I I mA ac hi eved arc disc ussed here. The synchrotron has a circumference of 2x.45 2 Description of the Facility m. It has a se parated functi on magnet ic lattice consisting or six superperiods , each havint> ;t The injec tor sys tem consis ts of a microtron, bending magnet and a quadrupole doublet. A multi­ sy nchrotron and tran sl'e r lines . The microtron turn injec tion sch eme ha s bee n c lw ~e n for injec ting provides an electron beam w ith a current of 25 mA electrons into th e sy nchrotron. T he ~c h e m e e mpl o y~ in Ips long pul se duration at a repetition rate of I three kickers to produce a compensa ted bump. The Hz. This beam is transported to th e synchrotron synchrotron has a harmonic nurnher or :i and " through Transfer Line- 1 (TL- 1-I ength 14m). Some repetition rat e of 1-2 H z. The elec trons injec ted ;tt 20 M eV are accelerated to 450 M eV in -200 ms. '·' Corres po nd ing au thor During this peri od, th e magnetic field of all ma gnets E- mai I: gurnam (nlc;tt.ern et. i 11 SINGH era/.: INDUS- I SYNCHROTRON RADIATION LJ7

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Fi g. I - La yo ut or Indus- I racility is in c reased in a programmed manne r to keep the magneti c lattice o f the ring has fo ur supe rpe ri m l:-­ e lectrons c irc ulating tn the sync hrotro n. The each consisting or a dipo le magne t w ith a fi e ld accele rated e lectrons are extracted using a fast inde x of 0 .5 a nd two pairs o r quadrupole douhlcl :--. kicke r having a ri se time o f -45 ns. During the Each superperiod has a 1.3 m lo ng straight secti on. extrac ti o n process. o ne out o f the three bunches is A n injecti on septum. injecti o n kicke r and RF cavit) lost and two bunc hes are extracted. These bunches are installed in strai g ht sections S I. S~ and S-L are transported through a Transfe r Line-2 (TL-2- respecti vely. A w iggle r w ill he installed late r in S2. Ie ngth 26 m) to the storage ring Indus-! . TL-2 To correct the natural c hromatic ity. a pair o r consists o r four quadrupole doublets and two sextupo les is used in each supe r-pe ri od. The nng be nding magnets to ta ke care o r the beam matc hing has a wide tuning range. require me nts at the po int of injecti on. The opti cs o r The beam injecti o n sche me e mployed in In dus- I the TL-2 has heen c hosen in such a way that the has one kicke r and one se ptum magne t and these arc beam s izes re main muc h less than the c hosen located at symmetri c po ints, diametricall y o pposi tL· vac uum c hambe r ape rtures w hil e satisfying the to each othe r. The injection procedure has been matc hing require me nt s. o ptimised by trac king motio ns o r the injected and Indus- I' is a 4.'i0 Me V e lectron storage ring the stored beams. In this sc he me, w he n the ki c ker i .~ designed to satisfy the use r require me nts in the e ne rgised , a bump is produced in the tnj ecti on range 10- IOO A. It is a small ring having a secti on. The ki cker g ives a max imum ki ck ang le o l" c irc umfe re nce o f 18.96 m. The photograph o r 18 mrad for a ki cker c urre nt o r 2500 A. The lndus- 1 s t or~ t ge ring is shown in fig . 2. The magneti c fi e ld in the ki c ker ri ses to a tTq uired value lJX INDIAN .I PURE & APPL PHYS. VOL 3lJ. JANUARY-FEBRUARY 200 1

Fig. 2 - Storage ring

111 I ~Ls following a sinusoidal shape and it decays overcome th e Robinson in stability driven by the ex ponentially wi th fall time of 150 ns. The kicker fundamental accelerating mode. curre nt is optimised in ord er to inj ect the beam at To understand the behaviour of th e beam during different tune points so that the betatron oscillation ramping, some experiments were carried out. amplitudes remain within the ho ri zontal aperture. Betatron tunes were measured usin g RFKO up to 3 Commissioning -300 MeV. The horizontal betatron tune was measured at the final e nergy using coherent The microtron was commissioned towards the excitation of the beam with th e help of th e end o f 1994. S in ce th e n it is regularly delivering a extraction ki cke r. The tune variation was very small 20 MeV beam of pulse current 25 mA, pulse le ngth during ramping. The horizontal tune at the inj ection of 1-2 ~s at a repetition rate o f I Hz. TL-1 optics energy was 2.22 18 and at the final e nergy was has also been o ptimised for thi s mi crotron beam and 2.220, the vertical tune at the inj ection e nergy was TL-1 is being used regularly for transfe r of 1.457 and at the 300 Me V it was 1.456 . Synchrotron e lectrons from the microtro n to the synchrotron. tune was measured during ramping. The coherent Beam emittance of the mi crotron beam was synchrotron oscillations were excit ed due to the measu re el in TL- 1. noise present on the signal used for cavity voltage Initially, the synchrotron was operated at the ramping. The synchrotron tune was 0.002267 at the injection energy to carry out some measurements. injection energy and it gradually decreased to As the currents in the magnets . were increased, the 0.0008823 at 450 MeV. The bunch le ngth at the beam was successfully accelerated to 480 MeV with final energy was measured using a wall current 1.8 mA beam current. At this time, the steering monitor. The bunch le ngth was 2cr, = 1.4 ns. With magnets were not e nerg ised. In subsequent this synchrotron tune and the measured bunc h operations, the current was increased to -I I mA length the momentum compaction of the machi ne mainly due to the correction of orbit using th e was estimated to be equal to 0 . 16 w hi c h is very horizontal and vertical steering magnets, ramping of close to the design value of 0 . 15 I. the RF voltage from 1.5-6.0 kV and possibly clue to Six Beam Position Indicators (BPI) are installed improvement in the field pattern of dipole magnets. in the sync hrotron (one per superperiod). The The RF cavity was de-tuned by -5 kHz with respect dispersion function at the BPI locations was to the generator frequency of 31 .6 16 MHz to obtained by measuring the change in the horizonta l SINGH et al.: INDUS- I SYNCHROTRON RADI ATION

s _ov : S On s

Fig. 3-Current signal in TL-2 and Indus- I without inj ecti on ki cker orbit with vari ati on in the RF generator frequency. noti ced that the beam spot used to shift hori zont all y T he measured values - 1.4 m are within I 0 % of the from time to time. This was mainly due to the design valu es at the BPI locatio ns. Beam positio ns dipo le current vari ati on (energy variati on) at the during rampi ng were moni tored . The orbit extracti on po int in the synchrotron. This proble m di stortion o f a few mm is record ed in the BPls. was rectified by extracting the beam at fixed dipo le current. The extracti on ki cker is sync hroni sed w ith To extract the beam fro m the synchrotron, the the dipo le extraction current. extracti on ki cker was e nergised to give a ki c k of -- I 0 mrad whi ch makes the c losed orbit Similar to the e xtracti on septum magnet o f the di splaceme nt o f -36 mm at th e e xtraction se ptum synchrotron, the inj ecti on septum mouth has al so locatio n. The ki cked beam was observed on th e been pa inted with a flu orescence material and is mouth o f the extracti o n septum magnet pa inted w ith viewed through a port. By adjusting th e steerin g ZnS. As th e local ion o f the septum is near th e magnets at the end o f TL-2, the beam spot was d ipo le magnet. th e intense synchrotron radiati on passed through the centre of the septum magnet. was stopped by a - 50 ~lm thin aluminium foil. C urrents o f the septum magnet, dipole and Usin g compe nsated c losed orbit bumps in e ither quadrupo les of Indus- ! were o ptimised to c ircul ate plane the beam was pushed into the septum the beam without the injecti o n ki c ke r and w ith RF aperture. T he two extracted bunches were cavity off. A beam spot was observed o n the BPM monitored in TL-2 usin g a Wall C urrent Pickup placed in S2 and maximum 6 turns were o bserved in (WCP). The curre nts in the quadrupo les in TL-2 the WCP pl aced in S3. Fi g. 3 indicates the presence were set ncar th e design currents initiall y and the of the extracted bunc hes at the beginning and at th e beam was transported up to inj ecti o n point o f Indus­ end o f TL-2 (TR2A,TR4A), the c irculation o f ! . During this passage, the beam was o bserved at 4 bunches for about 6 turns (TR3A) and the BPMs, viz BPMs located aft er extracti on septum, extracti on ki cker signal (TRI A). after BM I, be fo re third quadrupo le doublet and The real task o f beam injecti on trials to Indus- I aft er 8M2 in TL-2. The currents in th e quadrupo les began in April '99 immediate ly a ft er the in stallation were s li ghtl y changed for maximum transmi ssion of o f the inj ecti o n ki cker magnet int o the ring. Initially the beam. T he steering magnets (5 in the hori zontal by o perating th e ki cker at 1700A. beam c ircul ati on plane and 6 in the verti cal pl ane) were optimised to up to 30 turns was observed w ithout RF. O n centre the beam spot at the BPM screens as we ll as optimisation of the ki c ke r fi e ld and stre ngth s of the to maximi se th e current in the 2rr pi ckup monitor quadrupo lcs during subseque nt operati ons in the in stalled at the end o f th e line. Initia ll y it was 100 INDIAN .I PURE & APPL PHYS, VOL 39 , JANUARY-FEBRUARY 2001

:: - ·-~ ----- ~---. - - -~ ---· -·- . ------. ------· .. - ·- -· ----.- ---- ,. ------.

Fig. 4- DCCT signa l in Indus- I during initial hea m accu mul at ion

125ns 125ns 125ns l25ns

Fig. 5-Current accumulation in Indus- ! presence o f RF, beam storage began to take place accumulation in the ring was 161 mAi n July 1999 . but the beam accumulation was still not taking place Whereas the operational design current is I()() mA. smoothl y. It is shown in Fig. 4, where the injected The ring was o perated at different operating beam survives in the ring till the next pulse arrives points to study the beam lifetime and rate of filling. but the current is not increasin g continuously as the The rate of filling as observed during injection progresses. commissioning is s hown in Fig. 6. The beam was For successful accumulation of beam, the ki cker getting killed at the max imum accumulated current fi e ld had to be reduced so that both injected as well possibly due to collective beam in stabi li ty. as stored beam could survive during the injection The beam lifetime was initially poor due to the process. Fig. 5 shows the accumulated current degradation o f vacuum caused by the c leaning of (TR4A) al ongwith the injected beam at the end of the vacuum chamber by synchrotron radiation. As TL-2 (TR2A), the injecti on ki cker pulse (TR3A) the vacuum improved , the beam life time improved and the synchrotron extracti on kicker pulse (TRIA). to nearly one hour (calc ul ated for a current dccay The filling of the ring has been improved by from I 00 mA to 90 rnA ) at an average pressure o f optimising the parameters of the injecti on se ptum, I 0 nT. The beam lifetime in this case appeared to be kicker, quadrupo les, correcti on magnets and TL-2. governed by the vacuum. The bea111 lifetime w ill The fastest accumulation time to get a stored further improve as the vacuum pressure approaches curre nt o f I()() mA was -3 rni n at the operating I nTorr as required at the beam current of 100 mA. po int ( 1.69, 1.3 1). The maxtmum current The decay of the curre nt as shown hy the DCCT is shown in Fig. 7. SINGH et al.: INDUS- I SYNCHROTRON RADIATION I 0 I

"140

"1 20

"1 00 // // 80 / 2 0 //' 0

0 2 00 400 600 800 1000 Time (sec)

Fig. 6 - Filling in Indus- I

1 2 0

"100

80

~ 60 \~

c=C1> ~ 40 c..:> ~-~ 20 ·------0

0 2000 4000 6000 8000 "10000 12000 Ti~ (sec)

Fig. 7- Decay of current in Indus- I

the orbit. The dispersion function is -0.9m at these The betatro n tunes were measured by excltmg locations. The measured values of the average beta the beam using a Radio Frequency Knock Out functions and the dispersion function are within method. The tune point at which the maximum I 0 % of the theoretical values. The natura l curre nt has been achieved is measured as v, = 1.69. chromaticities are measured by c hangin g th e RF v, = 1.3 1. The paramete rs of Indus-! at this tune frequency and measuring th e c hange in th e betatron point are given in Table 2. The lattice functions are tune. The chro matic ities in x,z.- plane are -2.6,+3. 1. shown in Fig. 8. The difference between the measured and The beta functio ns at the quadrupole locations theoretical values is attributed to the presence or were obtained by measuring th e shift in the tune sextupole components in the dipoles. The ring is values by energising the secondary coils of the presently being operated without energising the focusing (Q1.)/de-focussing(Qn) quadrupoles. The chromaticity correcting sextupoles. The closed orbit average beta functio n at Qr/Qn in x-plane is 1.8 distortion is monitored at the BPI's locations. The m/ 1.3 m and in z. -plane is 1.4m/3.1 m. The orbit correction and o perati on of th e sextupoles are dispersion functions in the hori zontal plane at the planned during future runs of the ring. The attempts BPI locations were measured by changing the RF are being made to operate the rin g at other tune generator freque ncy and by measuring the change in 102 INDIAN .I PU RE & APPL PHY S. VOL 39. JANUARY-FEBRUARY 200 1

~- ·---.. '"'-""" ------~_;;_,__- - ....,.,..,--

0 ____j- ~ ,------·--.-~-~ -' , L'-

0 2 3 5 Pat:h Length (m)

Fig. X- Latti ce fun cti ons of Indus- I at ( 1.69. 1. 3 1) poi nts such as ( 1.55, 1. 56) and ( 1.88, 1.22) se lected present with out energtstn g the chromatic ity previously during th e design of the rin g. correctin g sextupoles. Operation in the presence. or these sex tupoles and correcti on of the closed orbi t is

T;1b le 2- P;~ram e ter s of tndu s- 1 pl ann ed. At present. th e li fe time in the storage rin g appears to be limited mainl y due to the vac uu m. Energy 450 MeV Current I 00 rnA With regul ar operation of the storage ring fo r few tachicvcd 161 mA) hours dai ly, the vacuu m wi ll improve further and Bending field 1.5 T consequ ently li fetime will also improve. Circumference IX.9(> m Cri tical w;~vclc n g th (> l .:lX ·' 11 Table) - Important dat es Photon tluxc 7.2 X 10 " Orer;Jting point I HJ. U l 00.04.99 )0 turn beam circu lation achieved 7 Be;~m em itt <~n ce (£J 1.5 x 10 ' m. racl I 0.04 99 SR light observed and beam storai!c ;Jchicvcd (R F 4 Energy srrcad 3.X 5 X I 0' cav ity switched on) M omentum co m r<~ c tion 0.2:15 10.0400 B e;~m acc umul ati on stilrted D<~mping times ( T,,~_,.) 15.7.15.7.7.X IllS OX.06.99 Beam current incre;1ses to I I :lmA Natu ral - 1.9 .-2 mA injection cuJ-renl Harmonic number 2 20. l()tJ!) Bea m lifetime 50 rnin 0>I 00 mA and 150 min Power los ~ 0.)(> kW @IOmA ·' bending magnet: ''Flux in photons/s/mr;Jd horz./0. 1% BW

5 Acknowledgements The important ela tes durin g ihe commi ss ioning The design and commt ss ionlll g of ln cl us- 1 of Ind us- I storage rin g are given in Table 3. fac ili ty is a teamwork or ma ny sciencists, engin eers and techni cal personn el of Accelerator Programme. 4 Conclusions CAT. The authors would li ke to thank all group The Ind us- I SR fac ilit y has been commi ss ioned leaders namely, P R Hannurka r. A Jain . M G 111 1999 with max imum accumul ated current of 16 1 Karmarkar, S Kotaiah, S K Shukl a, H C Soni , B .I mA. The inj ector system earli er commissioned has Vaid ya and their coll eagues fo r their contribution. bee n wo rkin g sa ti sfac toril y. The bea m dynami cs References ex periment s carri ed out on the storage rin g beam show th at th e meas ured para meters closely match Bhawiilkar D D e/ a/.. Pmu 'c'tlings o f' lntenwtinnol the des ign pa rameters. The machin e is run at S\'lllfWsium mt Medium /:,'ll('rgr Srncflmtmn Nwlimimt SINGH era!.: INDUS-I SYNCHROTRON RADIATION 103

Facilitit•s in Asia. (World Scicnlillc. Singapore). ( 1990). p. ( 1995). p 91. 16. 4 Sahon G K et of. . Proceedittg.1· o( .firs/ Asi(//t Porlit·f, . '2 Ramamurthi S S. Proceeding.\· o( In ternational Con/(•renn· Accelerator Con/(•rence. ( KEK. Tsukuha. Ja pan). ( Jl)l)X ). '"' Sl'llchmlmn Nadimimt soutn•s. Indore. ( 1992). p. lJ . p. 274 .

:1 An~a l D ('/ a/.. Proceedin gs o( 4th International 5 Singh G el a/.. Proceedings o( Conf(' l"l'II Cl' on srnclumron Conf(• n•nct• 0 11 SNS 's allll 2nd Asian Forum on SR. Korea . radiation atlfllicotiolls. (Hefei. China). ( Jl)XlJ ). p. 1'2'2 .