The source ECR2 has been built in 1998 by Pantechnik, according to the design suggested by LNS Ion Source Group. This design entails some improvements with respect to a standard CAPRICE-type source: a) the magnetic field (up to 1.6 T axial, 1.1 T radial) allows to operate the source at 14 GHz in High B mode and at 18 GHz; b) two frequency heating can be used; c) an aluminum made plasma chamber is used in place of the stainless steel one. The main features of ECR2 along with a review of the preliminary tests will be outlined. Typical currents for fully stripped nitrogen are about 25 emA; for the heaviest ions, 1 emA of Kr28+ and 10 emA of Ta27+ have been measured. The installation at LNS has been completed recently and the details will be given

Bieth, C

Castro, M

Celona, L

Chines, F

Ciavola, G

Gammino, S

Kantas, S

Marletta, S

Sortais, P

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INSTALLATION OF ECR2 AT LNS AND PRELIMINARY TESTSS. Gammino   , G. Ciavola, M. Castro, L. Celona, F. Chines, S. MarlettaINFN-Laboratori Nazionali del Sud, Via S. Sofia 44, 95123 Catania, ItalyC. Bieth, P. Sortais, S. KantasPantechnik S.A., rue A. Kastler 12, 14000 Caen, FranceAbstractThe source ECR2 has been built in 1998 by Pantechnik; itis an ECR4M, modified according to the suggestions of theIon Source Team of LNS. The main improvements are:a) a higher magnetic field (up to 1.58 T axial, 1.1 T radial)is used, to operate the source at 14 GHz in High  Bmode and at 18 GHz with a quite good confinement;b) two frequency heating can be used, by means of amixer;c) an aluminum made plasma chamber is used in place ofthe stainless steel one;d) the maximum voltage is 30 kV.The main features of ECR2 along with a review of thepreliminary tests will be outlined.The installation of the source at LNS has been completedrecently and some details will be given.1 THE SOURCE DESCRIPTIONThe source ECR2 is the latter upgraded model of the well-known CAPRICE ECR ion source [1] which evolutionthroughout the years have marked the development of theECR sources, with different versions, CAPRICE 14 GHz atGrenoble [2], ECR4-M at GANIL [3], Hypernanogan atManne Siegbahn Laboratory, built by Pantechnik.With respect o these sources, ECR2 has some majorimprovements, as described in the abstract: in particular, theAl chamber, which has been used during the acceptancetests, has significantly increased the currents, as observed inother laboratories [4,5].Operating frequency 14 and 18 GHzMaximum radial field on the wall 1.1 TMaximum axial fieldat injection1.25 T (for 14 GHz)1.58 T (for 18 GHz)Maximum axial fieldat extraction1.0 T (for 14 GHz)1.35 T (for 18 GHz)Minimum axial field 0.4 T (for 14 GHz)0.5 T (for 18 GHz)Coils supply Two 1300 A – 60 VHexapole NdFeB madeExtraction system Accel-decel,35 kV/12 kV maxPlasma chamber St. steel or Al madeTab. 1 – Design parameters of LNS-ECR2.The three-electrode extraction system has not been usedextensively with the plasma during the preliminary tests atLNS, but it is ready to be used, while 18 GHz operationsand two-frequency heating can be tested only in the secondpart of this year. The axial field profile can be scaled withthe frequency and the magnets allow operating at 18 GHzwith one of the highest confining field yet achieved byconventional ECR ion sources. The maximum field is 1.58T, as a compromise between the requirements of high axialfield for High B mode operations and the maximum powerfrom the supply (which is quite large, about 180 kW). Ahigher field would have been useful for 18 GHz operations,as observed for SERSE [6], but the requirements in terms ofpower would have been prohibitive.In tab. 1 the main parameters of the source are given. Twophotos of the source are shown in fig. 1 and 2.Fig. 1 – The LNS- ECR2 source.2 THE TESTS AT GANIL TESTBENCHWe carried out on the testbench a first set of ests withstainless steel chamber, for gaseous elements (Ar, O, Kr),and metals, by oven (Ca) or by sputtering (Ta, Ni); thestability over 4 hours was measured for Ta and Ni andemittance measurement were carried out for Ar, O, Kr andTa. A second set of tests was carried out with an Aluminumchamber, only with gaseous elements (Ar, O, Ne, 15N)including some emittance measurements, in presence of alarge extracted current.The optimum magnetic field used for these tests (at 14 GHz)was slightly different for the different ion species, beinghigher on the injection side, for the highest charge states(about 1.2 T) while at the extraction it was about 0.8 T.2.1 – Tests with the stainless steel chamberThe tests with Argon were carried out with the goal toachieve currents exceeding 80 eµA of Ar11+ and 10 eµA ofAr14+, which are the typical performances of Hypernanoganfor routine operations.These value were obtained after a short optimization and thiswas really encouraging, being these speci s considered asreference ions for the production of medium charge states andhigh charge states respectively.Fig. 2 – The ECR2 source on its support stand.Similar results were obtained for Oxygen, which currents of80 eµA for O7+ and 530 eµA for O6+ were largely above thespecifications and close to optimum performance forCaprice-type source. In fig. 3 one of the best charge statedistribution for Krypton high charge states is shown; it canbe observed that 22 eµA of Kr20+  and 10 eµA of Kr22+  wereproduced, that is a relevant result with respect to the otherCAPRICE-type sources. Emittance measurements werecarried out for O7+  and Kr22+, that have given values of RMSin the order of 60 to 80 p mm mrad for 90% of the beam inboth cases, in good agreement with the results in literature[7,8]. Fig. 4 shows a typical emittance plot for O7+.The source was opened, in order to insert an oven on axis,able to get a maximum temperature of 1500 °C. It wasoperational (vacuum was in the mid 10-7 mbar) after onenight and a stable beam was obt ined after six hours ofconditioning with plasma. For sake of brevity, tests werecarried out only with Calcium ions, for which is quitecomplicate to obtain a stable oven regime.The optimization gave stable currents of 30 eµA for Ca12+and 3 eµA for Ca14+. A trial to further enhance the currentsof the highest charge states led to values exceeding 50 eµAfor Ca12+  and 5 eµA for Ca14+ but the source was not stable.01 02 03 04 05 09 0 100 110 120 130Beam current (eµA)Dipole current (A)Krypton17+18+19+20+22+Fig. 3 – A charge state distribution, optimized for Kr22+.Fig. 4 – Emittance plot for O7+.Tests for Tantalum ions were prepared initially with theevaporation method, but we observed that a bias voltage onthe Tantalum wire allowed to increase significantly thecurrents, especially for the highest charge states, accordingto the sputtering method elsewhere developed [9].The measured current for Ta28+ w s above 7 eµA and forTa31+ it exceeded 3 eµA (fig. 5), which is a larger value thanCAPRICE best results. The stability over 4 hours wasexcellent (better than 5%) but the emittance was high (about150p mm.mrad). Tests for Nickel were not so satisfactory,because the peak current was larger than expected (7 eµA forNi19+) but the beam was not stable and after one hour only itwas necessary to tune the source again. The wireconsumption was too large, then the distance between theplasma and the wire is to be increased and a larger wire (tostabilize the sample temperature and limit the emission ofclusters) must be used.01020304050100 110 120 130 140Beam current (eµA)Dipole current (A)Tantalum24+25+26+27+28+29+31+Fig. 5 – A charge state distribution optimized for Ta31+.010020030040050070 80 90 100 110 120 130 140Beam current (eµA)Dipole current (A)7+8+6+9+11+12+13+14+Argon, Al chamberFig. 6 – A charge state distribution, optimized for Ar11+.0200400600800100072 80 88 96 104 112 120 128Beam current (eµA)Dipole current (A)Oxygen6+3+5+7+Fig. 7 – A charge state distribution, optimized for O6+.2.2 - The tests with the Aluminum chamberThe stainless steel chamber was dismounted and replaced byan Aluminum chamber, with the same shape anddimensions, according to the experience reported in [4,5].The tests were carried out with a maximum power of 600 Wfor the whole duration of tests, except a short period, whenthe power was increased to 750 W (this chamber was nevertested with plasma and we had some concerns about itsrobustness, but it is to be remarked that after the end oftests, the inspection of the chamber gave positive results andno evidence of overheating was found out). The tuning withthe Aluminum chamber was even easier because thealuminum wall is a source of “cold” electrons, whichdecrease the plasma potential [4].05010015020025030035040072 80 88 96 104 112 120Beam current (eµA)Dipole current (A)6+3+5+7+4+NitrogenFig. 8 – A charge state distribution, optimized for N7+.Ion GANIL-ECR4M LNS-ECR2N5+ 500 515N6+ 120 16015N7+ - 25O6+ 700 720O7+ 100 105Ne7+ - 230Ne8+ - 170Ne9+ - 14Ar11+ 200 120Ar14+ 15 10Ar16+ 1 2Ca12+ 60 52Ca14+ 12 6Ni17+ 10 18Kr22+ 10 10Kr28+ 0.1 1Ta26+ 5 10Ta27+ 4 10Tab. 2 – Typical currents produced ECR4M and ECR2The same performances are obtained with lower power,because of the smaller electron losses, and the average chargestate increased as effect of the higher ion lifetime.Fig. 6 shows a charge state distribution, optimized for Ar11+,which peak is above 120 eµA, 30% higher than the currentsobtained with stainless steel chamber. For Ar14+ m re than10 eµA were obtained with a power below 0.75 kW,whereas more than 1.1 kW were necessary for the samecurrent with the stainless steel chamber. Fig. 7 showsacharge state distribution optimized for O6+ (more than 700eµA, and more than 100 eµA for O7+). It is reasonable toexpect that higher currents be obtained with higher power.Two tests were carried out explicitly for the EXCYT project[10]. The first consisted of the optimization of Ne9+ forwhich  quite high value (14 eµA), close to the goal ofEXCYT, was obtained. When the current was optimized forNe8+, it exceeded 170 eµA, with 230 eµA of Ne7+ and 400eµA of Ne6+.The second test was about 15N7+, for which the higher wasthe RF power, the higher was the current of 15N7+, above 20eµA for a power of 700 W (fig. 8). More than 160 eµA of15N6+, were measured with the same tuning. With a typicaltuning for medium charge states (lower magnetic field andhigher pressure), the currents were above 500 eµA for thecharge state 5+ and 400 eµA for the 4+. In tab. 2 the resultshereabove described are compared with the best onesmeasured on ECR4M during years of operations. It comesout that the insertion of the Aluminum chamber hasconsiderably increased the capability of the source to producehigh current of high charge states, which is the primary goalof ECR2 design. It is to be pointed out that the duration ofall tests with Al chamber was about one day, so that there isstill room for large improvements.3 THE INSTALLATION AT LNSThe source was installed at LNS in March 1999 and onMarch 19th the first beam was obtained. We started with thethree-electrode system and a rather rough alignment of thesolenoid and of the 90° analyzing magnet, because part ofthe vacuum beam pipes was not timely delivered (thealignment procedure  is now under way). Once that theconditioning of the source was completed, typical currentswere a factor two below the current  measured on thetestbench. We expect to settle all these problems, once thatthe beamline will be completed, and the optimum vacuumand alignment will be obtained.The analysis beamline after the source is a copy of the oneof SERSE [6], consisting of a solenoid, focusing the beamto the object point of the 90° analyzing magnet, after whichthe axial injection beamline to the K-800 SuperconductingCyclotron [11] begins. Fig. 9 shows the area where ECR2is installed. The 14 GHz generator is located close to thesource and put aside the main coil supply. The 18 GHzgenerator is available nearby. The installation of ECR2 atLNS have obliged us to plan carefully every positioning,because in the same area it is present SERSE with itscryogenic equipment. I  addition, the accomplishment ofsome particular equests, concerning the high pressurecooling water for the coils and large power from mains, havebeen crucial for the success of the installation of the source.4 CONCLUSIONSIt can be concluded that the preliminary source tests havebeen satisfactory and that already the source performsreasonably well, in comparison with the other CAPRICE-type sources, in spite of the short duration of the tests.Moreover the other options described in th  abstract willcertainly allow significant improvements, and even if wecannot expect that this source achieve the results of SERSE,anyway its flexibility will certainly be advantageous forroutine cyclotron operations, because of the short timeneeded for the opening of the source and for anymaintenance. Once that alignment will be completed, finaltests will be accomplished, with a particular emphasis onthe production of metallic ions, which will be the main taskof ECR2. While SERSE will be used for the highest chargestates and the highest currents, ECR2 will be devoted to thefrequent changes of metallic ions, because of its flexibilityand short time for dismounting/mounting that will behelpful in order to satisfy a strict Cyclotron schedule.The source will be connected to the K-800 SuperconductingCyclotron by the end of summer 1999.Fig. 9 – ECR2 beamline.5 ACKNOWLEDGEMENTSThe authors thank O. Tasset, E. Robert, E. Messina fortheir support to the preparation of the test here described.6 REFERENCES[1] F. Bourg et al., Nucl. Instr. & Meth. A254 (1987) 13[2] D. Hitz et al., Proc. 11th Workshop on ECRIS, KVI (1993), 91[3] P. Sortais, Rev. Sci. Instr. 67 (3), 1996, 867[4] Z.Q. Xie and C.M. Lyneis, Proc. 12th Workshop on ECRIS, RIKEN(1995), 24[5] D. Hitz et al., Proc. 12th Workshop on ECRIS, RIKEN (1995), 126[6] S. Gammino et al., these proceedings[7] R. Leroy et al., Rev. Sci. Instr. 67 (3), 1996, 1350[8] T. Antaya et al., al., Proc. 11th Workshop on ECRIS, KVI (1993), 37[9] R. Harkewicz et al., Proc. 12th Workshop on ECRIS, RIKEN (1995),19[10] G. Ciavola et al., Proc. of 1999 Part. Acc. Conf., New York, in press [11] D. Rifuggiato et al, “First years of operation with theSuperconducting Cyclotron”, Proc. of the 15th Conf. on Cyclotrons andAppl., Caen, June 1998, in press

Installation of ECR2 at LNS and Preliminary tests

Installation of ECR2 at LNS and Preliminary tests

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