John Robert Torczynski- Second Sound Shock Waves in Rotating Superfluid Helium
NUSTAR-5 Design and construction of a superfluid-helium stopping cell
description
Transcript of NUSTAR-5 Design and construction of a superfluid-helium stopping cell
DIRAC Midterm Review, GSI, December 2006 NUSTAR-5, C. Scheidenberger
Involved institutes:
* JYFL, Jyväskylä* GSI* KVI (not as contractor)
NUSTAR-5 Design and construction of a superfluid-helium stopping cell
DIRAC Midterm Review, GSI, December 2006 NUSTAR-5, C. Scheidenberger
Objective
• Design of a cell, operated with superfluid helium, for the stopping of energetic radioactive ion beams. Tests and performance study with a prototype using radioactive beams available in Jyväskylä
5 cm
43210
SourceBottom electrode
Guidingelectrodes
Focusing electrode
Collector foil
Detector holder
alphadetector
electrodes
foil
DIRAC Midterm Review, GSI, December 2006 NUSTAR-5, C. Scheidenberger
Present status (1)
219Rn trapped at the surface
0.20
0.15
0.10
0.05
0.00
21
9R
n c
ount
rate
(/s
)
16012080400
peak pulse height (V)
1.05 K
7.2(6) % extractionefficiency
7.2(6) % extractionefficiency
219Rn extracted fromthe surface
219Rn extracted fromthe surface
needs confirmation
NiCrheater
alpha detector
Al foil-200 V
electrode520 V
223Ra540 V
DIRAC Midterm Review, GSI, December 2006 NUSTAR-5, C. Scheidenberger
Present status (2)
35 35
30 30
25 25
20 20
15 15
10 10
5 5
0 0
effi
ciency
(%
)
140 100 60 140 100 60180 140 100 60
temperature (K)
helium neon argon
28.7(1) %
22.1(2) %
17.0(2) %
- Proposed stopping cell dimensions may also be reached using a cryogenic gas catcher (T≤20 K) * 20 K technically less demanding than <2 K * ions do not need to cross the boundary between the liquid- and gas-phases
- 2×3 days of beam time used in 2005 * technical problems in the liquid helium cell tests * cryogenic helium gas catcher (77 K) tests gave promising results
freezing out of impurities workstechnically easier than ultra-pure at room temperature
fundamental upper limitthe measured efficiencies are determined by the cross sections
DIRAC Midterm Review, GSI, December 2006 NUSTAR-5, C. Scheidenberger
Present status (3)
Recent measurements at JYFL overlayed on a compilation of other results
Extraction efficiency of helium gas ion catchers as a function of ionisation rate, as presented by D.J.Morrissey at the SMI-06 Workshop, Groningen, the Netherlands, March 27-28, 2006
DIRAC Midterm Review, GSI, December 2006 NUSTAR-5, C. Scheidenberger
Deviation from original workplan
1) Delay:Tests done earlier this year at Jyvaskyla with the cryostat from KVI failed partly due to a technical problem (leak)
instead: measurements with the cryogenic gas catcher
2) New concept:Already stressed in January meeting, progress since then, tests in 2007,looks very promising
DIRAC Midterm Review, GSI, December 2006 NUSTAR-5, C. Scheidenberger
Outlook on completion
KVI: the study of the superfluid liquid-helium catcher will be pursued at KVI (off-line developments aiming at fast and efficient extraction via second sound waves), feasibility has to be demonstrated
JYFL:* study of cryogenic gas catcher will be pursued at JYFL, development of a system for on-line tests underway (drawings being prepared, construction starts early 2007)* confirm the off-line results and test the transport of ions from cryogenic cell to vacuum* proposal accepted, beam time in preparation
GSI:* beam time request under preparation
program will be finished within ~ 1 year