Transcript Recent progress in the WITCH experiment

WITCH:
studies made in 2005
S. Coeck
M. Herbane, V.Yu. Kozlov, I.S. Kraev, N. Severijns, F. Wauters
M. Beck, P. Delahaye, A. Herlert, F. Wenander
The ISOLDE, NIPNET and TRAPSPEC collaborations
In collaboration with: LPC-Caen and University Mainz (K. Blaum)
WITCH: studies made in 2005 06/02/06
Sam Coeck
Weak
Interaction
Trap for
CHarged particles
Overview
• Motivation and overview of WITCH
• Where we left off in 2004
• Pulsed Drift Tube
• MCP detectors
• Conclusion and outlook
WITCH: studies made in 2005 06/02/06
Sam Coeck
Motivation for WITCH
Fermi b-decay: H = HV(CV, C’V) + HS(CS, C’S)
Standard model: V=1, S=0 (a=1) ; experimentally: S<8%
S>0 -> a<1 (a = b-n angular correlation coefficient)
a=1
Recoil spectrum
a=1/3
a=0
a=-1/3
a=-1
WITCH: studies made in 2005 06/02/06
Sam Coeck
Overview of the setup
~7m
WITCH: studies made in 2005 06/02/06
Sam Coeck
Going for radioactive ions
Monday 8/11/2004 (evening) – Thursday 11/11/2004 (morning):
First run of WITCH with radioactive 35Ar
Problem:
 Problem with ISOLDE target (CaO)
Result: factor of 40 (in the beginning 400) less 35Ar
and a lot of 35Cl
 The efficiency of the injection into the traps is not high
enough yet to handle this
WITCH: studies made in 2005 06/02/06
Sam Coeck
Efficiency overview
ideal
reality
HBL
PDT
100%
43%
100%
8% (*)
Magnetic field injection
Capture cooler trap
Losses during cooling
Transfer between traps
100%
100%
100%
100%
1%
60%
75%
80%
100%
40%
10% (**)
100%
60%
100%
?
?
?
52%
1%
0,0006%
Losses in second trap
Recoil ions leaving the trap to spectrometer
Shake-off charge state
Transmission through spectrometer
MCP efficiency
Total
(*) might be underestimated by factor ~5
(**) can be increased to ~80% by using b- decay
WITCH: studies made in 2005 06/02/06
Sam Coeck
Pulsed Drift Tube (PDT)
70cm
WITCH: studies made in 2005 06/02/06
Sam Coeck
Understanding the PDT
WITCH: studies made in 2005 06/02/06
Sam Coeck
Understanding the PDT
WITCH: studies made in 2005 06/02/06
Sam Coeck
MCP saturation problems
Misinterpretation of:
• total intensity
• relative intensity
• time structure
• tuning
Solution:
• limit incoming intensity
directly or using attenuating grid
• limit operating voltage
to avoid this saturation
WITCH: studies made in 2005 06/02/06
Sam Coeck
Position sensitive diagnostics
• Slow
• Inaccurate position information
• Can be difficult to quantify
• Fast (1 wire / pulse for now)
1 full scan / pulse possible
• Higher spatial resolution
• Still gives timing information
• Simple
WITCH: studies made in 2005 06/02/06
Sam Coeck
Conclusion
• Behavior of PDT is now better understood
• MCP saturation effects have been studied and can be avoided
• New diagnostics system has been implemented
• Various ideas concerning improving the efficiency are ready to be tested
• Construction of own ion source has been started, this to gain independance
• Tests with new position sensitive recoil ion detector (LPC-Caen) are ongoing
• Extensive simulation work has been done on various aspects of the set-up
WITCH: studies made in 2005 06/02/06
Sam Coeck
Outlook for 2006
• Further testing of the PDT and injection in the magnetic field (coming weeks)
• Further optimize beam diagnostics
• Testing + installation of WITCH 60keV
39K
ion source
• Testing of the isobaric purifying power of the cooler trap
• Optimizing buffergas circuit for Penning traps
• Installation of the new position sensitive recoil ion detector
• Test possible background from b-particles on recoil ion detector
• First ‘proof of principle’ experiment
Thank you for your attention
WITCH: studies made in 2005 06/02/06
Sam Coeck