On-line tests RFQ coolerISCOOL
A quick summary
P. Delahaye, H. Frånberg,I. Podadera
ISCOOL, COLLAPS, ISOLDE collaboration
Principle
RFV
Three elements:RF quadrupolar fieldRadial confinement
DC potentialsExtracting ion in bunches or in continuos mode
Buffer gas Ion motion cooling
Emittance measurements• Without cooling • With cooling
~35·mm·mrad 95% emittance
~2.2·mm·mrad 95% emittance
Transmissions• Potentials along the axis
• Transmissions in DC – 23Na: 50%– 39K: >75%– 85Rb: >75%
Better than the off-line tests!Smaller emittances from ISOLDE surface ion sources than from the ion source used during off-line tests.
80eV5-2V/cm
~1E-2 mbar 4He10-2mbar l/s
EXTRACTIONINJECTION
50V (30V enough)
TRAPPING
Cooling time• TOF < 1ms from the entrance to the exit of
the RFQ
• 1 passage is enough to get a cold beam – as measured off-line, and other labs as
predicted by simulations for other systems
-200 0 200 400 600 800 1000 1200 1400 1600 1800-1
0
1
2
3
4
4.0x10-4
6.0x10-4
8.0x10-4
1.0x10-3
1.2x10-3
1.4x10-3
1.6x10-3
Bea
m g
ate
Time [s] M
CP
Bunching mode
30keV
80eV5-2V/cm
~1E-2 mbar 4He10-2mbar l/s
EXTRACTIONINJECTION
50V (30V enough)
TRAPPING
Space charge limits
• Up to 108/s!! As measured with FC (data under analysis with MCP)
0.00E+000 1.00E+009 2.00E+009 3.00E+009 4.00E+009 5.00E+009
0.00E+000
2.00E+007
4.00E+007
6.00E+007
8.00E+007
1.00E+008
1.20E+008
1.40E+008
Ext
ract
ed
ion
s
Injected ions
39K
0.00E+000 4.00E+008 8.00E+008 1.20E+009-2.00E+007
0.00E+000
2.00E+007
4.00E+007
6.00E+007
8.00E+007
1.00E+008
1.20E+008
1.40E+008
1.60E+008
Ext
ract
ed io
ns
Injected ions
85Rb
Bunch width• Depends on the space charge and cooling
time
Collection / cooling time
-40 -20 0 20 40 60 80 100 120 140
-8x10-3
-7x10-3
-6x10-3
-5x10-3
-4x10-3
-3x10-3
-2x10-3
-1x10-3
0
1x10-3
2x10-3
MC
P s
igna
l
Time [s]
10 ms 100 ms 1000 ms
Preliminary results
• Data from 26Na needs to be analyzed
• Losses due to trapping time (analysis in progress)
• Chemistry, noble gases, reactive elements
• More data needed for more masses (light ions)– CaO target + plasma ion source should
provide some answers
-7 -6 -5 -4 -3 -2 -1
0
20
40
60
80
100
120
140
160
180
200
Gat
ed c
ount
s
Tuning voltage
-7 -6 -5 -4 -3 -2 -1
490000
492000
494000
496000
498000
500000
502000
Tot
al c
ount
s
Tuning volts
ISCOOL TEST46K Beam 1E5 ions/s after the cooler. Collection time 20 minutes, with 300ms bunching and a 12us gate and 2mW of laser power.
Singles (continuous counting)Bunched:12us gated spectra
Background suppression factor~1E4