The GTS-LHC ion source, designed and build by CEA Grenoble, was installed and commissioned at CERN in 2005. Since than the source has delivered oxygen and lead ion beams (O4+ and Pb27+ from the source, Pb54+ from the linac) for the commissioning of the Low Energy Ion Ring (LEIR). Results of this operation and attempts to improve the source performance and reliability, and the linac performance will be presented in this paper

Dumas, L

Hill, C

Hitz, D

Küchler, D

Mastrostefano, C

O'Neill, M

Scrivens, R

CERN Document Server

EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH European Laboratory for Particle Physics   CERN CH - 1211 Geneva 23 Switzerland  Geneva, Date   Large Hadron Collider Project   LHC Project Report 985 Operation of the GTS-LHC Source for the Hadron Injector at CERN L. Dumas1, C. Hill1, D. Hitz2, D. Küchler1, C. Mastrostefano1,  M. O’Neil1 and R. Scrivens1   Abstract  The GTS-LHC ion source, designed and build by CEA Grenoble, was installed and commissioned at CERN in 2005. Since than the source has delivered oxygen and lead ion beams (O4+ and Pb27+ from the source, Pb54+ from the linac) for the commissioning of the Low Energy Ion Ring (LEIR).  Results of this operation and attempts to improve the source performance and reliability, and the linac performance will be presented in this paper.   1ABP/AB, CERN, 1211 Geneva, Switzerland                                                                 2SBT/DRFMC, CEA, 17 rue des Martyrs, 38054 Grenoble, France  Presented at the 17th International Workshop on ECR Ion Sources and their Applications, ECRIS’06 September 17-21, 2006, IMP, Lanzhou, China  Operation of the GTS-LHC Soure for the Hadron Injetorat CERNL. Dumas, C. Hill, D. Hitz, D. Kühler1, C. Mastrostefano, M. O'NeilandR. SrivensCERN, AB/ABP/HSL, 1211 Geneva 23, SwitzerlandCEA, DRFMC/SBT. 17 rue des Martyrs, 38054 Grenoble edex 9, FraneAbstrat. The GTS-LHC ion soure, designed and build by CEA Grenoble, was installed and ommissioned at CERN in2005. Sine than the soure has delivered oxygen and lead ion beams (O4+and Pb27+from the soure, Pb54+from the lina)for the ommissioning of the Low Energy Ion Ring (LEIR).Results of this operation and attempts to improve the soure performane and reliability, and the lina performane will bepresented in this paper.Keywords: operation, linear aelerator, metal ions, bias diskPACS: 07.77.Ka1. IntrodutionA part of the physis programme of the Large HadronCollider (LHC) is dediated to heavy ion ollisions.Within the last years the injetor hain was upgraded andmodied to ensure the beam properties needed for theheavy ion operation of the LHC. As part of an intensityimprovement the old ECR4 soure was replaed by theGTS-LHC soure [1℄.Detailed informations onerning the installation andthe ommissioning of the soure are published in [2℄.Sine the middle of 2005 the soure and Lina3 wererunning most of the time for the ommissioning of theLow Energy Ion Ring (LEIR) and its injetion line. Therewas only some limited time to study the soure itself andto improve their performane.2. Operational experienesFor the ommissioning of LEIR and its injetion lineLina3 had to deliver oxygen and lead ion beams.For the ommissioning with oxygen, O4+had tobe used (similar q/m as Pb54+). To injet the beamin the RFQ the extration voltage had to be set to10 kV (orresponds to 2.5 keV/u). The soure deliv-ered 300 emA under these onditions, 120 emA weretransmitted through the RFQ and at the end of the lina70 emA were available.The beam was very stable overseveral weeks. After the stop of the soure for inspetiona strong erosion of the extration eletrodes was found.1detlef.kuhlerern.hFor the ommissioning with lead, a Pb27+beam fromthe soure was aelerated and stripped to Pb54+. Duringthe ommissioning of the soure a urrent of 215 emAould be reahed for a short time in Faraday up 2 (seeFigure 1). But for a stable, longterm operation only up to104 emA in Faraday up 3 ould be reahed, whih gaveat the end of the lina up to 17 emA of Pb54+.FIGURE 1. Sketh of the Low Energy Beam Transport(LEBT) of Lina3.A typial harge state distribution from the soure isshown in Figure 2.After the LEIR set-up some optimisation of Lina3inreased the urrent out of the lina to 30 emA for aurrent of 100 emA of Pb27+in Faraday up 3 for ashort period.A study was made of the extration gap between theplasma eletrode and intermediate eletrode (for all mea-surements the distane between the intermediate and theground eletrode was kept onstant). For eah gap a va-uum intervention was neessary beause the gap lengthould not be hanged remotely. The soure was opti-mised every time for three days, so the long term effet ofthe different gaps was not studied. The results shown in70 75 80 85 90 95 100spectrometer current/A0100200300400500ion current/eµALead afterglow05/08/05, 1000W, 1270A/343A/1250APb26+/O2+Pb25+Pb24+Pb23+Pb22+Pb27+Pb28+Pb29+Pb30+Pb31+Pb32+FIGURE 2. Lead harge state distribution from the soure.TABLE 1. Ion urrent in Faraday up 3, horizontaland vertial emittane versus length of the soure extra-tion gap. The emittane is simulated with KOBRA3D.It is the rms value for the Pb27+beam, the intermediateeletrode is at -1kV.gap/mm 35 40 45 50Ion urrent/emA 118 104 124 102e (horizontal)/mmmrad 160 130 130 140e (vertial)/mmmrad 180 200 190 170Table 1 show a maximum intensity (transmitted throughthe RFQ) with a gap of 45 mm, in omparison to the40 mm gap used during the LEIR ommissioning.Some simulations were done with KOBRA3D(Figure 3, Table 1). The aeptane of the LEBT is200 mmmrad [3℄. The simulation results annot fullyexplain the optimum extration gap length of 45 mm.FIGURE 3. Simulation of the extrated lead beam for a gaplength of 45 mm. (The beam onsists of the omplete hargestate distribution as in Figure 2. The ion density distributionwas modelled star-shape like)The lead onsumption during operation ould be re-dued to less than 1 mg/h, allowing the soure to run forat least 14 days between oven rells. For ECR4 this timewas 3 to 4 weeks.3. Bias disk experimentsDuring the rst setting up of the oxygen beam it hasbeen found that the beam transport in the Low EnergyBeam Transport (LEBT) part of the lina (Figure 1) wasstrongly dependent of the setting of the bias disk voltage.Zavodszky et al.[4℄ showed that the transverse emit-tane of the ARTEMIS soure for the O3+beam in-reases with inreasing bias disk voltage. Unfortunatelythere is no diret possibility to measure the emittaneat Lina3. For an indiret measurement the transmissionbetween Faraday up 2 and Faraday up 3 (see Figure 1)was determined. The aeptane of the elements betweenthe two Faraday ups is in this ase the limiting fatorfor the transport, and this ould give an estimation of themaximum emittane.-500 -400 -300 -200 -100 0bias disk voltage/V0100200300ion current/eµAFC2FC3FIGURE 4. O2+ion urrent in Faraday up 2 and 3 forpulsed RF and bias disk voltage.-500 -400 -300 -200 -100 0bias disk voltage/V0100200300400500ion current/eµAFC2FC3FIGURE 5. O2+ion urrent in Faraday up 2 and 3 for RFand bias disk voltage in w.The rst experiments were done with O2+. The Fig-ures 4 and 5 show the ion urrent in the Faraday ups2 and 3 for pulsed and w operation of the RF and thebias disk voltage. It is learly visible that with higher biasdisk voltage the urrent in Faraday up 2 inreases, but-500 -400 -300 -200 -100 0bias disk voltage/V00.10.20.30.40.5ratio ion current FC3/FC2RF and BD pulsedRF and BD cwFIGURE 6. Transmission of the O2+ion beam betweenFaraday up 2 and 3.-400 -300 -200 -100 0bias disk voltage/V00.20.40.60.81ratio ion current FC3/FC2BD pulsedBD cwFIGURE 7. Transmission of the Pb27+ion beam betweenFaraday up 2 and 3.this urrent an't be transported down to Faraday up 3(Figure 6). The effet is worse for w operation of thebias disk voltage.Further experiments were done with Pb27+in after-glow mode. Figure 7 shows the transmission of the leadion beam. In omparison with oxygen the transmission-400 -300 -200 -100 0bias disk voltage/V020406080100ion current FC3/eµABD cwBD pulsedFIGURE 8. Pb27+ion urrent in Faraday up 3 for pulsedand w bias disk voltage.is muh higher but there is still a slight dependene fromthe bias disk voltage. Figure 8 shows the ion urrent inFaraday up 3 as a funtion of the bias disk voltage andthe operation mode (pulsed or w). In general the pulsedmode gives more urrent than the w mode. For higherbias disk voltage the wmode even redues the afterglowmode ion urrent. The large variations of the ion urrentbetween -200 V and -300 V in the pulsed mode are dueto instabilities during the ion pulse (see also Figure 9b).The ion urrent jumped between two stable states.FIGURE 9. Traes of the lead ion beam in Faraday up 3 fordifferent bias disk voltages. (trae 1: bias disk voltage, trae 2:ion urrent, trae 3: RF pulse)Figure 9 shows some traes of the lead ion beammeasured in Faraday up 3. Figure 9a shows the normalafterglow (only a time slie of 700 ms is transportedthrough the RFQ). Figure 9b shows the enhanementof the afterglow for -100 V bias disk voltage, but itshows a instability during the pulse. Figure 9 shows theoptimised pulse, with a high intensity and a smooth pulseshape.The result of this experiments give some guidane forfurther soure set-ups. Even if the ion urrent out of thespetrometer (in Faraday up 2) is maximised this shouldnot mean that a maximum urrent out of the RFQ (inFaraday up 3) or out of the Lina3 an be expeted. Theoptimisation of the soure for the lina operation shouldtherefore be done with Faraday up 3 and after the lina.The stabilisation of the afterglow pulse and the en-hanement due to the pulsed bias disk voltage were al-ready reported for experiments with the ECR4 soure [5℄and are now onrmed with the GTS-LHC soure.4. ConlusionThe ommissioning of LEIR was suessful and theearly beam for the LHC heavy ion operation ould beprepared. The soure showed a good performane andreliability and most of the problems shown up during thesoure installation and ommissioning ould be solvedmeanwhile.The behaviour of the beam from the soure as a fun-tion of the bias disk voltage showed some interestingeffets. A reprodution on another soure in afterglowmode with some emittane measurements is neessary.Also a theoretial model how the bias disk voltage in-uenes not only the beam intensity but also the beamquality is needed.REFERENCES1. C.E. Hill, D. Kühler, R. Srivens, D. Hitz, L. Guillemet,R. Leroy, J.Y. Paquet. GTS-LHC: A New Soure ForThe LHC Ion Injetor Chain. AIP Conf. Pro. 749 (2005)127-130.2. C.E. Hill, D. Kühler, C. Mastrostefano, M. O'Neil,R. Srivens, D. Hitz, L. Guillemet, J. Chartier,J.M. Mathonnet, G. Rey-Giraud. Experiene with theGTS-LHC Ion Soure. Pro. 3rd LHC Projet WorkshopChamonix XV (2006) 239-241.3. N. Angert et al. CERN Heavy-Ion Faility Design Report.CERN 93-01, 1993.4. P.A. Zavodszky, H. Koivisto, D. Cole, P. Miller. EmittaneStudies Of ARTEMIS  The New ECR ION Soure ForThe Coupled Cylotron Faility At NSCL/MSU. AIPConf. Pro. 576 (2001) 619-622.5. C.E. Hill, D. Kühler, F. Wenander, B.H. Wolf. Effet ofa biased probe on the afterglow operation of an ECR4 ionsoure. Rev. Si. Instrum. 71 (2000) 863-865. 1 

Operation of the GTS-LHC Source for the Hadron Injector at CERN

O'Neil, M

Operation of the GTS-LHC Source for the Hadron Injector at CERN

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