Program to improve the ion beam formation and transmission at JYFL University of Jyväskylä, Department of Physics H. Koivisto, T. Ropponen, J. Ropponen, T. Koponen, M. Savonen, V. Toivanen, P. Heikkinen Michigan State University, National Superconducting Cyclotron Laboratory G. Machicoane, J. Stetson, P. Zavodszky, X. Wu, M. Doleans, S. Chouhan Gesellschaft fur Schwerionenforschung (GSI), Darmstadt, D-64291, German P. Spädtke KVI, Groningen, Netherlands H. Beijers and S. Brandenburg,
Beam transport at JYFL: Background IGISOL (Ion Guide Isotope Separator On-Line) Our challenges (concerning the beam intensity): RITU (Recoil Ion Transport Unit) We are not always able to meet the intensity requirement
Reference beam Background (concerning beam transmission development work) Presently 8 µa available after cyclotron (10 kv extraction voltage, second harmonic) Goal: at least douple the available beam intensity
Statistics (2004) Total transmission efficien 0,18 JYFL 14 GHz ECRIS 2nd harmonic 0,16 0,14 0,12 0,10 0,08 0,06 0,04 0,02 I cycl /I ECR 0,00 0 25 50 75 100 125 150 175 Intensity [µa] 14 GHz ECRIS Transmission efficiency decreases when the beam intensity from the ECRIS increases!
Measured transmission efficiency of K130 cyclotron facility (typical behavior) K130 extraction efficien 120 110 100 90 80 70 60 50 40 30 20 10 0 0,700 Ar8+ intensities after ECRIS and cyclotron 0,600 0,90 after ECRIS 0,80 after cyclotron 0,70 0,500 0,60 0,400 0,50 0,40 0,300 0,30 0,20 0,200 0,10 0,100 0,00 0,000 0 20 40 60 80 100 120 2 Ar8+ intensity from ECRIS [µa 0 1 2 3 4 5 6 7 8 Measurement Transmission efficiency to inflector 14 12 6 4 0 Intensity from cyclotron [µa] Typical Ar 8+ ion beam transmission efficiency as a function of intensity extracted from the JYFL 14 GHz ECRIS. Conclusion: problem between the ECRIS and 10 the inflector! 8 What is wrong? - originates from plasma? - beam formation? 0 20 40 60 80 100 Ar8+ intensity from ECR> - beam transport?
Beam line Better DIMAD-simulations to start from beam (By transport! Dr. X. Wu/NSCL): What has been found (for example)? Beam viewer - Wrong entrance/exit angle of dipole Asymmetric beam
DIMAD simulations (by X. Wu) at this point Horizontal plane/bending plane (parallel beam) Vertical plane (diverging beam)
DIMAD simulations (by X. Wu) Beam spot in viewer according to DIMAD-simulations Beam spot in viewer (just after dipole)
Comprehensive experiments have to be performed in order to improve beam transport!! 20 mm collimator requires fairly strong focusing! This effect increases with: - focusing strength - beam intensity - stronger for lower q
Conclusion so far: it seems to us that two reasons for the transmission behavior has been found! 1) Asymmetric beam - wrong entrance/exit angle of dipole 2) Hollow beam - space charge effect? - hollow beam is formed in the ECRIS (proposed by P. Spädtke)? In addition: Transport efficiency in the case of third harmonic acceleration is poor (50 % compared to 2nd harmonic)
How to improve the beam transmission? 1) Make the beam symmetric! - new dipole with correct entrance/exit angle or - add quadrupoles to correct the beam 2) Make uniformly distributed beam - understand how the hollow beam is formed? 3) Add beam viewers and beam profile instruments into the beam line Next step: the beam formation in ECRIS extraction!!
Other activities of ion source group 1) Development of metal ion beams (new ovens, sputtering, MIVOC, etc...) 2) Electron heating simulations, Bremsstrahlung, coupling of microwaves, 3) Better ion sources, more beam (european collaboration...complecs/fp7), - take care of the beam quality and beam transmission!!
Development of metal ion beams Several ion beams which require temperature above 1500 C 1. Resistively heated foil oven have been asked! -> technique has to be improved - Above 2000 C Reliability has to be improved: -mechanical connections seem to be a problem -> temperature fluctuation from run to run)
Inductively heated oven 2000 C has been reached with the home made resonant circuit (P. Suominen and M. Savonen) 22 mm Life time and durability tests have been started Very stable in the test bench (1820 C ± 2 for several days)