Transcript In-trap spectroscopy

JYFLTRAP:
Spectroscopy with multi-trap facility
• Facility
• Mass purified beams
• In-trap spectroscopy
• Future plans
JYFLTRAP Layout
IGISOL beam
Spectroscopy set-up
RFQ-cooler/buncher
Penning traps
Spectroscopy with purified beams
RFQ cooler buncher and purification trap
MRP 20 000 ... 150 000
Cycle time down to 100 ms
Total transmission ~ 10 %
Maximum intensity tens of thousands/bunch
Example A=112
Coming experiments: Ga, Zr
Example A=112 fission products
2500
A = 112
4 MeV
Rh (6.8/2.1 s)
2000
Counts
1500
MRP=72 000
1000
Ru (1.8 s)
500
0
960120
960140
960160
960180
960200
960220
960240
Frequency [Hz]
Frequency scan over cyclotron frequencies of
112Rh, ions are detected with MCP.
Mass difference is about 4 MeV.
Cycle time 450 ms.
MRP = 72 000.
112Ru
and
Test results A=112
b-gated g-spectrum
collected in one hour.
112Rh and 112Ru were
produced in proton
induced fission.
100000
No excitation
- + c
348.7keV, Rh112
10000
359.7keV, Rh112
388.2keV, Rh112
327keV, Ru112
N
1000
100
10
1
300
320
340
360
380
Energy [keV]
Total trap cycle 450 ms
340 ms cooling
15 ms dipole excitation f-=1705 Hz/160 mV
90 ms quadrupole excitation fc=960190 Hz/150 mV
400
Mass resolving power
A=112 fission products
Simulated frequency scans over fission products with different MRP
MRP = 70 000
MRP = 30 000
16
Rh
30
Rh
14
Pd
Ag
25
20
10
15
Ions a.u.
Ions a.u.
Pd
Ag
12
Ru
8
Ru
6
10
4
5
Mo
2
Tc
Mo
0
959900
Tc
0
960000
960100
Frequency (Hz)
960200
960300
959900
960000
960100
Frequency (Hz)
960200
960300
Experiments along N=Z line
Example 62Ga (t½=116ms)
From old IGISOL 400 ions/s (reaction 64Zn(p,3n)62Ga, Ep= 48MeV, Ip=35mA)
2-10 ions/s purified beam with present transmission
MRP 20 000 is enough to separate 62Zn and 62Cu from 62Ga
Ions a.u.
14000
A=62
12000
64Zn(p,x)
10000
MRP = 20 000
8000
Zn
Cu
6000
4000
2000
Ga
0
1734600 1734700 1734800 1734900 1735000 1735100 1735200 1735300
Frequency (Hz)
Simulated frequency scan
Improving the trap extraction
SIMION simulations for mass A=100 q=+1 ions
Implantation
point
Second einzel lens added to
improve transmission to the
spectroscopy setup.
Problematic place in
extraction. Ions follow
magnetic field lines.
Cut one long electrode in the
end of magnet region into two
to squeeze the ion trajectories
at the point where magnetic
field lines start to diverge.
Present geometry
30 mm
Planned improvement
2.5 m
Challenges
Transmission through the trap system (5 - 20 %)
Cooler transmission has been poor since last summer (only ~30%)
Install Si detectors to improve diagnostics
Extraction from the magnetic field; ions tend to follow field lines
Divide one electrode
Shorter cycles (less than 100 ms)
Find limit for Ions per bunch; space charge limit
In-trap spectroscopy
• Trapped ions form an ideal source without any
scattering or energy loss in source material.
• Lineshape
• Peak-to-background ratio
• Strong magnetic field of a penning trap can be used to
transport charged particles (e, p, a, ...) to the detector
with high efficiency.
• Conversion electrons etr ~ 50%
• Energy and mass selection with trajectory radius rtr
• In average electron rtr< proton rtr
• Conversion electron rtr < beta rtr
In-trap detector set-up
Detector:
Canberra RD EB10GC-500P
Thickness 500 mm
Active area 10 mm2 (r = 1.78mm)
Dead layer 250 Å
PA1201 Pre amp
Resolution less than 1 keV for
59.5 keV X-ray from 241Am source and
1.5-2 keV for electrons from 131Ba source
Source ions trapped in the
purification trap.
Source to detector distance ~60cm.
Simulated transport efficiency ~50%
up to 300keV.
In-trap plans
Near future
• Selecting a good test case, good yield, t½, electron energy, conversion
coefficient
• Trap scheduling
• Beamtime for testing
• First physics proposal: neutron rich Zr decay spectroscopy
Open questions
• How to tune the trap injection when the ejection side is blocked by the
detector ?
• How to arrange data acquisition because detector sits on HV platform ?
Later
• Segmented detector to avoid summing and allow coincidence detection
Outlook and conclusions
Purified beams
JYFLTRAP is ready to make purified beams for spectroscopy
Mass resolving power is enough for most of the cases
Transmission needs still improving
Systematic tests of the high intensity limit together with short cycle time
In-trap spectroscopy
Mechanical parts are ready
Data acquisition not yet designed
First test hopefully during next summer
IGISOL facility
IGISOL upgrade is almost ready. Improved yields have been recorded with
light-ion ion guide.
Laser ion source project has been started to improve ion guide efficiency
and also to introduce chemical selectivity.