Techniques and challenges of ion beam preparation A. Jokinen - PowerPoint PPT Presentation

Techniques and challenges of ion beam preparation A. Jokinen Department of Physics, P.O.Box 35 (YFL) FIN-40014 University of Jyväskylä Measurement, After production target or post-accel. products of interest Ion (beam) manipulation filter other products primary beam Beam = Purification + Manipulation preparation Sub-Task 1 Sub-Tasks 2 and 3 EURISOL-DS; Task 9, Beam preparation: The objective of this task is to study the feasibility of a new generation of devices with orders of magnitude greater capacity and throughput in order to accumulate, cool, bunch and purify the high intensity radioactive ion beams of EURISOL. (+ Construction of the prototype for beta-beams) EURISOL UG Workshop CERN – JYFL – LMU – MSL – INFN – CSNSM - LPSC Firenze, Italy, January 2008

Manipulation of radioactive ions Ion group (beam,cloud) properties Ion properties energy energy degrading • charge state ionization stopping, trapping • ionic/atomic state acceleration optical pumping • energy spread • spin direction cooling, trapping alignment polarization • emittance cooling • size cooling, trapping • time structure pulsing bunching “ion beam cooler” “charge breeder” (gas-filled RF quadrupole) (ECRIS & EBIS) Sub-Task 2 Sub-Task 3 EURISOL UG Workshop Firenze, Italy, January 2008

Target and ion source tricks • Neutron converter � removal of spallation products – Absolute yield lower – Compensated by the selectivity (purity) • Molecular sidebands � reduction of contaminants – Transfers products to new clean mass region – No laser ionization • Ion guide approach (IGISOL) � access to refractory elements – No chemical selectivity – Fast – Overall efficiency low • Laser ionization � chemical selectivity (Z) – Enhancement of chemical selectivity – Isomeric selectivity • Laser ion source trap (LIST) – Reduction of contaminants � enhanced selectivity EURISOL UG Workshop Firenze, Italy, January 2008

Molecular sidebands Another example: Spectrscopy of n-def. Sr isotopes produced from Nb-target and extracted as SrF molecule � No target-produced background (especially Rb !) EURISOL UG Workshop Firenze, Italy, January 2008

Target and ion source tricks • Neutron converter � removal of spallation products – Absolute yield lower – Compensated by the selectivity (purity) • Molecular sidebands � reduction of contaminants – Transfers products to new clean mass region – No laser ionization • Ion guide approach (IGISOL) � access to refractory elements – No chemical selectivity – Fast – Overall efficiency low • Laser ionization � chemical selectivity (Z) – Enhancement of chemical selectivity – Isomeric selectivity • Laser ion source trap (LIST) – Reduction of contaminants � enhanced selectivity EURISOL UG Workshop Firenze, Italy, January 2008

IGISOL at JYFL Thin target approach for refractory isotopes: IGISOL (Ion Guide Isotope Separator On-Line) Neutral atom Beam Ion Target He-inlet 10 -4 10 -6 p [mbar] 100 1 10 kV 30 kV 500 V EURISOL UG Workshop Firenze, Italy, January 2008

Target and ion source tricks • Neutron converter � removal of spallation products – Absolute yield lower – Compensated by the selectivity (purity) • Molecular sidebands � reduction of contaminants – Transfers products to new clean mass region – No laser ionization • Ion guide approach (IGISOL) � access to refractory elements – No chemical selectivity – Fast – Overall efficiency low • Laser ionization � chemical selectivity (Z) – Enhancement of chemical selectivity – Isomeric selectivity • Laser ion source trap (LIST) – Reduction of contaminants � enhanced selectivity EURISOL UG Workshop Firenze, Italy, January 2008

LIST (Laser ion source trap) Coupling to isotope Ion/atom Repeller separator source electrodes Ion trap Laser beams - Atoms exiting the source are selectively ionised by the lasers - Ions produced in the source repelled back - >selectivity boost K. Blaum et al ., - Laser-atom interaction length = v atom /laser rep. rate Nucl. Instr. and Meth. B204, 331 (2003) - Radial overlap over the interaction length critical for efficiency ISOLDE: diffusion/effusion of neutrals out from the source IGISOL: gas jet transport of neutrals out from the gas cell EURISOL UG Workshop Firenze, Italy, January 2008

Magnetic separation (HRS at ISOLDE) EURISOL UG Workshop Firenze, Italy, January 2008

Basics of magnetic separation EURISOL UG Workshop Firenze, Italy, January 2008

Optimization of mass purification EURISOL UG Workshop Firenze, Italy, January 2008

Sub-1: EURISOL-HRS Multiple multipolar dipoles Large dispersion Corrections (T. Giles, CERN) EURISOL UG Workshop Firenze, Italy, January 2008

Purification in the Penning trap Recipe: Dipole excitation to blow up the radial motion of all ions Mass-selective centering of wanted ions by resonance quadrupole excitation 1400 101 Mo 101 Nb 1200 101 Zr 1000 FWHM = 20 Hz 800 M/ Δ M = 145 000 Counts 600 400 101 Y 200 0 1064700 1064750 1064800 1064850 1064900 Frequency [Hz] • FWHM ~ 20 Hz • m/ δ m = 145000 possible (above spectrum m/ δ m ~ 53000) V. Kolhinen et al., NIM A528 (2004) 776 • sufficient for mass spectroscopy S. Rinta-Antila, PRC 70 (2004) 011301(R) • ”Experimental approach”, • RIB-facility use demonstrated at REX-ISOLDE EURISOL UG Workshop Firenze, Italy, January 2008

Trap-assisted spectroscopy 10000 The first new decay Rh Pd Ag scheme observed: 115 Ru 1000 115 Ru Counts 100 MRP 30000 10 T exc 121 ms 1 0 50 100 150 200 250 300 350 Frequency [+934900 Hz] A=115 with ω c ( 115 Ru) A=115 from IGISOL J. Kurpeta et al. EPJ A 31 (2007) 263 EURISOL UG Workshop Firenze, Italy, January 2008

Sub-2: Ion cooling and bunching in linear Paul traps (D. Lunney) EURISOL UG Workshop Firenze, Italy, January 2008

Ion beam cooler: principle • reducing beam size, emittance, energy spread • storing • bunching (not chopping !) the output does not depend on the input ! principle reducing energy spread: thermalization in (He) gas RF confinement by E-fields + • RF multipole • Axial electrodes _ _ + + EURISOL UG Workshop Firenze, Italy, January 2008

Present RFQ-devices Name Input Beam Input Cooler Length R 0 RF Voltage, Freq, DC Mass Axial Voltage Pressure Output Beam Qualities Emittance Range Colette 60 keV ISOLDE beam ~ 30 π -mm- 504 mm (15 segments, 7 mm Freq : 450 – 700 kHz -- 0.25 V/cm 0.01 mbar He Reaccelerated to up to 59.99 keV decelerated to ≤ 10 mrad electrically isolated) with long. energy spread ~10 eV eV LPC Cooler SPIRAL type beams Up to ~ 100 468 mm (26 segments, 15 mm RF : up to 250 Vp, Freq : -- -- up to 0.1 mbar -- π -mm-mrad electrically isolated) 500 kHz – 2.2 MHz SHIPTRAP SHIP type beams 20- -- 1140 mm (29 3.9 mm RF: 30-200 Vpp, Freq: 800 up to 260 Variable: 0.25 ~ 5×10-3 mbar -- Cooler 500 keV/A segments, electrically kHz – 1.2 MHz amu – 1 V/cm He isolated) • Plenty of devices prototyped JYFL Cooler IGISOL type beam at Up to 17 π - 400 mm (16 10 mm RF: 200 Vp, Freq: 300 kHz -- ~1 V/cm ~0.1 mbar He ~3 π -mm-mrad, Energy spread < 4 40 keV mm-mrad segmentes) – 800 kHz eV • Similar devices in size and operation parameters MAFF Cooler 30 keV beam -- 450mm 30mm RF: 100 –150 Vpp, Freq: 5 -- ~0.5 V/cm ~0.1 mbar He energy spread = 5 eV, Emittance decelerated to ~100 MHz @ 30keV: from = 36 π -mm-mrad to • Different solutions for the electrode structures to eV eT = 6 π -mm-mrad ORNL Cooler 20-60 keV negative ~50 π -mm- 400 mm 3.5 mm RF: ~400 Vp, Freq: up to -- up to ±5 kV ~0.01 mbar Energy spread ~2 eV provide transverse and axial confinement RIBs decelerated to mrad (@ 20 2.7 MHz on tapered <100 eV keV) rods LEBIT 5 keV DC beams • Perform very well : δ E < 1 eV, dt ~ few μ s, e ~ few π -- -- -- -- -- -- ~1×x10 − 1 mbar -- Cooler He (high-p sect.) mm mrad, on-line efficiencies 80 % ISCOOL 60 keV ISOLDE beam up to 20 π - 800 mm (using 20 mm RF: up to 380 V, Freq: 300 10-300 ~0.1V/cm 0,01 - 0,1 mbar -- mm-mrad segmented DC wedge kHz - 3MHz amu He electrodes) • Not optimized for high intensities ! (EURISOL-DS) ISOLTRAP 60 keV ISOLDE beam -- 860 mm (segmented) 6 mm RF: ~125 Vp, Freq: ~1 -- -- ~2×10-2 mbar elong ≈ 10 eV us, etrans ≈ 10p mm Cooler MHz. He mrad. TITAN RFCT continuous 30–60 -- -- -- RF: 1000 Vpp, Freq: 300 -- -- -- 6 π -mm-mrad at 5 keV extraction keV ISAC beam kHz - 3 MHz energy TRIMP TRIMP beams -- 660 mm (segmented) 5 mm RF= 100 Vp, Freq.: up to 6 < A < -- up to 0.1 mbar -- Cooler 1.5 MHz 250 SPIG Leuven IGISOL Beams -- 124 mm (sextupole rod 1.5 mm RF= 0-150 Vpp, Freq.: 4.7 -- -- ~50 kPa He Mass Resolving Power (MRP)= cooler structure) MHz 1450 Argonne -- -- -- -- -- -- -- -- -- CPT cooer SLOWRI -- -- 600 mm (segmented 8 mm RF= 400 Vpp, Freq.: 3.6 -- -- ~10 mbar He -- cooler sextuple rod structure) MHz EURISOL UG Workshop Firenze, Italy, January 2008