F. Schwellnus 1 , T. Gottwald 1 , C. Mattolat 1 , V. Sonnenschein 1 , K. Wendt 1 ,
description
Transcript of F. Schwellnus 1 , T. Gottwald 1 , C. Mattolat 1 , V. Sonnenschein 1 , K. Wendt 1 ,
Off-line Tests and first On-Line Installation Off-line Tests and first On-Line Installation
of the Laser Ion Source Trap LISTof the Laser Ion Source Trap LIST
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Application for Test of CVC and CKM Unitarity Application for Test of CVC and CKM UnitarityF. Schwellnus1, T. Gottwald1, C. Mattolat1, V. Sonnenschein1, K. Wendt1,
R. Catherall2, B. Marsh2, F. Österdahl3, V. Fedosseev2,
K. Blaum1,4, H.-J. Kluge4, S. Schwarz5
1 Institut für Physik, Johannes Gutenberg Universität Mainz
2 CERN Physics Department
3 Department of Physics, Royal Institute of Technology, Stockholm
4 Gesellschaft für Schwerionenforschung, Darmstadt
5 NSCL, Michigan State University, East Lansing
Proposal to the INTC, 21. May 2007
INTC Meeting 21.05. – 22.05.2007
OverviewOverview
• The idea:
Development of an ion source which combines very high selectivity with
excellent control over the ion beam properties.
• The basis:
The successfull joint material and laser tests for RILIS
at the off-line separator in Jan. 2007
• The method:
Combination of the advantages of a laser ion source with those
of a radio frequency quadrupole cooler and buncher.
• The physics case:
Test of CKM unitarity and constant vector current hypothesis CVC by mass
measurements on 62Ga and 62Zn using ISOLTRAP
• The proposal:
Request for off-line and on-line beam time on 62Ga & 62Zn at ISOLDE in 2008
INTC Meeting 21.05. – 22.05.2007
Motivation for RILIS & LIST
1. Atomic Beam Source
3. Mass Separator 4. Laser System
Proton Beam
Ion Repeller
to Experiments
Laser- Beams
HV Platform
ISOLDE RILIS
Source
IonBeam
Ti:Sa 1
Ti:Sa 2
Ti:Sa 3
Nd:YAG
Laser System
Mass Separator
with Surface Ion Reppeler
Gas filledRFQ Trap
2. Gas filled RFQ Trap Section for Bunching and Cooling
Production of isobarically pure ion beams with optimum spatial and
temporal ion pulse control using a gas-filled RFQ structure
INTC Meeting 21.05. – 22.05.2007
Principle of the LISTPrinciple of the LIST
Electron Repeller
Ion Repeller
Z
Release
10 mmEnd Plate
SIMION 7.0: simulation of the potential distribution
Laser IonsSurface Ions
UDC
Atomizer
Electrons
Laser BeamsAtoms Ions
SwitchableElectrodes
RFQ SegmentsRFQRFQ SegmentsSegments
Accumulate
Helium Buffer Gas ~ 10-3 mbar
Laser Ionization
Electron Repeller
Ion Repeller
Z
Release
10 mmEnd Plate
SIMION 7.0: simulation of the potential distribution
Laser IonsSurface Ions
UDCUDC
Atomizer
Electrons
Laser BeamsAtomsAtoms IonsIons
SwitchableElectrodes
RFQ SegmentsRFQRFQ SegmentsSegments
Accumulate
Helium Buffer Gas ~ 10-3 mbar
Laser Ionization
INTC Meeting 21.05. – 22.05.2007
Technical RealizationTechnical Realization
LIST prototypes developed and characterized in off line tests @ Mainz RISIKO MS
LIST 1 LIST 2 LIST 3 (in preparation)
Efficient resonance ionization via an all-solid state Ti:sapphire laser system:
INTC Meeting 21.05. – 22.05.2007
60 kV RISIKO Mass Separator @ UMz
ISOLDE 2 Frontend
UMz Ti:Sa laser system
Orsay EmittanceMeter
60 kV RISIKOMass Separator
@ IPhy, UMz
INTC Meeting 21.05. – 22.05.2007
Pump laser: Photonics Industries Nd:YAG, 532 nm, >80 W at 10 kHzTunable lasers: 2 single & 1 double sided UMz Ti:Sapphire lasers
- frequency doubling, tripling and quadrupling- computerized temporal and spectral control - efficient ionization of 19 elements demonstrated
tested or in user at: IKch&IPhy@UMz, TRIUMF, JYFL, Oak Ridge, LLN, ISOLDE, UNagoya
commercialized at the International Laser Fair, Munich, June 2007
Mainz Ti:Sapphire Laser Setup Mainz Ti:Sapphire Laser Setup
INTC Meeting 21.05. – 22.05.2007
Characterization of Prototype PerformanceCharacterization of Prototype Performance
LIST 2
Prototype dimensions:
Length: 10 cm
Diameter: 6 cm
Field Radius: 0.5
cm
fitting into ISOLDE target
Tests of different modes of operation:
• Ion guide, without bunching
• Bunching, low intensity, sharp beam energy (< 1 eV)
• Bunching, high intensity, broad beam energy (> 1 eV)
Important parameters for characterization:
• Overall ionization efficiency
• Isobaric selectivity via surface ion suppression
• Spatial emittance
• Energy distribution
• Temporal structure of ion bunches
INTC Meeting 21.05. – 22.05.2007
Distance between source and trap Efficiency
10 mm ~ 1·10-5
5 mm > 3,2·10-5
0 500 1000 1500 2000 2500 3000 3500
0
50
100
150
200
250
300
350
FC
curr
ent /
pA
time / s
4,391012 atoms of 69 Ga collected
6.271012 atoms of 69 and 71 Ga
21017 atoms placed in oven
= 3.1410-5
LIST operation as ion guide without buffer gas or trapping,
surface ion repeller voltage optimized for selectivity
LIST Efficiency in the Ion Guide Mode
Efficiency curve Temporal profile on peak
INTC Meeting 21.05. – 22.05.2007
-2000 0 2000 4000 6000 8000 10000 12000 14000 16000 18000
0
500
1000
1500
2000
FC
Str
om
/ pA
Zeit / s
1.16 1014 Atome Ga 69 und 71 insgesamt
davon 9,71 1012 Atome nichtresonant ionisiert
resonant
= 5.35 10-4
Optimization of Efficiency with LIST 2
Incomplete suppression of background from
too high atomic vapor density in trap:
- collisional ionization
- electron bombardment ionization
- field and black body ionization
INTC Meeting 21.05. – 22.05.2007
Efficiency
2 cm atomizer
Suppression
of surface ions (K/Ga)
Time structure
Trap capacity
Emittance
LIST RILIS@UMz
derived from RILIS and LIST Measurements in Ga @ RISIKO, UMz
5,1·10-5 1,5·10-2
> 1000 -
> 106 ions / shot -
~ 5 s > 50 s
~1.5 mm mrad
Specifications of LIST 2
• Efficiency is fully determined by atomic beam collimation and atomizer length
2 cm oven length
4 cm oven length
~1.0 mm mrad
INTC Meeting 21.05. – 22.05.2007
LIST Geometry and Ionization Efficiency
segmented, linear quadrupole
(filled with He - buffergas)
repeller
electrodes
extraction-
lenses
ionization region
atomic beam source
lasers
extraction region
extraction
electrode
• High Efficiency via well collimated atomic beam & low ionization rate before trap volume
• Optimum value so far: LIST ~ 1% of RILIS efficiency
further improvements of atomic beam source in progress
INTC Meeting 21.05. – 22.05.2007
rms 1,3 mm·mrad
Emittance Measurements Laser vs. Surface Ions Emittance Measurements Laser vs. Surface Ions
rms 1,0 mm·mrad10-7 10-6 10-5 10-4 10-3 10-2 10-1
1,2
1,4
1,6
1,8
2,0
2,2
2,4
2,6
2,8
rms
em
ittance
/ P
i mm
mra
d
buffer gas pressure / mbar
Cooling Time 0.5 ms 1 ms 2 ms
Results from Orsay emittance meter
@RISIKO, UMz, April 2007,
LIST in ion guide mode
Simulations for bunching using
Simion 3D & LISBUN
INTC Meeting 21.05. – 22.05.2007
ISOLDE 2 front end preparation for LIST targetISOLDE 2 front end preparation for LIST target
INTC Meeting 21.05. – 22.05.2007
Placement of the LIST within the ISOLDE target Placement of the LIST within the ISOLDE target unitunit
INTC Meeting 21.05. – 22.05.2007
LIST Status and ISOLDE Beam Requests
OFF-line tests:
UMz Ti:Sa laser system operation at off-line Separator in Jan./Feb. 2008
First characterization of ISOLDE LIST target on Ga, Ca, Ni and Mn
Request for 4 weeks of off-line separator use during winter shut down
in close exchange and collaboration with ISOLDE ion source crew
On-line investigations:
On-line installation & use of first ISOLDE LIST ion source on ZrO2 target
15 shifts in spring/summer 2008 for LIST characterization and 62Ga
12 shifts on autumn 2008 for LIST refinement and 62Zn
using LIST/ZrO2 target/ion source combination with laser ionization
INTC Meeting 21.05. – 22.05.2007
Maximum Ion Storage Capacity
• High importance parameter in case of high production rate of neighboring isotopes
• Integral ion beam 0,2 nA, Trap rate 350 Hz, 5 Lasershots on, 15 off, p = 3.8·10-4 mbar
• Maximum loading capacity: 4·106 Ions / cooling cycle
Loss of reasonable ion pulse time profile
40 50 60 70 80 90 100 110 120 130 140 150
0
20
40
60
80
100
120
Co
un
ts
ToF / s
Maximum loading capability
60 65 70 75 80 85 90
0
200
400
600
800
1000
1200
Cou
nts
ToF / s
Few ions in LIST trap
~10 µs
~ 2 µs
INTC Meeting 21.05. – 22.05.2007
Time StructureTime Structure
20 40 60 80 100 120 14029990
29995
30000
30005
30010
30015
30020
potentialset 1 potentialset 2 potentialset 3
Po
ten
tial /
V
z-axis / mm
60 70 80 90 100 110 120 130 140
0
1000
2000
3000
4000
5000
6000
potentialset 1 potentialset 2 potentialset 3
Co
un
ts
tof / s
20 40 60 80 100 120 140
-2
0
2
4
6
8
10
Po
ten
tial /
V
z-axis / mm
Potentialset 1 Potentialset 2
Trap closed
20 40 60 80 100 120
0
10
20
30
40
50
60
Potentialset 1 Potentialset 2
Counts
tof / s
FWHM 8.2 s
width > 60 s