View
216
Download
0
Category
Preview:
Citation preview
CCC Project at GSI- Update
Febin KurianGSI Helmholtzzentrum für
SchwerionenforschungGermany
Contents
• Highlights of the CCC at GSI – from the past
• Beam current measurement with CCC – Spring
2014
• Measurements planned for September 2014
• Conceptual schematic of the new CCC system
• Some hints for a new cryostat design
GSI-CCC Cryostat: First Concept
• Possibility of test measurements offline and also within the beam line.
• Possibility of complete and easy dismantling of the cryostat and the equipment therein
• Low liquid helium consumption - Manual filling of LHe is difficult especially when installed in the beam line – one filling should be enough for complete experimental session.
• Should have a more or less fixed cycle time including (cooling down- experiments- warming up)
Existing CCC system at GSI
100 mm
381 mm
352 mm
658 mm
710 mm
1200
mm
GSI Facility
CCC installation location
Beam current measurements with CCC
Plan of the measurement• Characteristics of the newly installed SQUID sensor
system and electronics
• Noise figure of the CCC system
• Vibration analysis of the experimental set up
• Measurement of the beam current
• Comparison of the measured currents with a different system (in our case, Secondary Electron Monitor)
Supracon SQUID + Magnicon ElectronicsI-V Characteristics
1µA/div
200m
v/di
v
• Transfer co-efficient of the SQUID,
• Current needed in the feedback coil to produce one ; () = = 10.66 µA
• Gs, Gain of the SQUID
• With a Gain bandwidth product = 0.38GHz, the system bandwidth,
Gs. GBP
For the best settings, Rf@FLL was set at 30 KΩAmplification of the SQUID given - 2000
V-ɸ Characteristics
50mv/div20
0mv/
div
50 nA Test pulse signal measured by CCC (noise floor – 2 nA)
Current Calibration
CCC- pickup coil
Low pass filter- Cut off frequency = 170 Hz
Noise Spectrum
Current Calibration Curve
Voltage- Current conversion factor=74.2 nA/V
Current Measurement Scheme
Oscilloscope/FFT
SQUID
Amp. T,P,LCurrent Source
SQUID Control
Diff. Amplifier
SIS18
DCCT
CCCSEM
Al foils
Femto DHPCA 100transimpedance amplifier.
GM cooler unit
H.V
Measurement room
Femto Amp control pc- Remote access
Current Measurement-1
Output signal contains,• Signal from the DCCT installed in SIS 18• CCC differential output -- blue and red• SEM signal
Example of a raw output signal shows the beam current of about 3E9 particles of Ni26+ with energy of 600 MeV extracted from SIS18 over 1 second (Mean current – 12.5 nA)
Current Measurement-2
Beam current signal by 7E8 particles of Ni26+ with energy of 600 MeV extracted from SIS18 over 500 millisecond (Mean current – 5.5 nA)
Current Measurement-3
Smallest signal measured by CCC of 2.5E8 particles of Ni26+ (Mean current – 1.9 nA)at 600 MeV extracted over 500 millisecond
Current measurement-CCC and SEM
Comparison of the spill structures given by CCC and SEM when measuring the current of5E9 particles extracted over 64 ms giving an average current of 210 nA
DCCT, CCC and SEM signals
Current Estimation from plotsCCC• The differential output voltages signals C2 and C3 are
combined by the equation
• From this output voltage, the current is estimated by
A- Area of the integral (Baseline corrected)
SEM• The current produced by the secondary electron,
The term is estimated to be 43.7 from the “SRIM” program
Integral of the spill gives ,
Current measurements with CCC and SEM-1
SEM result is shown without a multiplication factor to obtain equivalent current (Presently used factor shows discrepancies with the current values measured by CCC)
In Smaller range
Special Conditions
• Presence of “Anti-Alias filter”• SQUID signal is filtered with a low pass filter at the magnicon
amplifier with cut-off frequency of 10KHz
• Optically isolated differential amplifier• Output amplification of 10: 2 differential• Differential output• Cut-off frequency 200 KHz
• SEM- Bandwidth depends on amplification factor given at the femto amplifier - 220 kHz at 108 to 200 MHz at 103.
Measurement planned for Sept. 2014
• Measurement over wider bandwidth (without the filter at the Magnicon electronics)
• More measurements on the intrinsic current resolution of the CCC.
• Wider range of the beam current/ extraction time
• More set of SQUID adjustment – Rf @FLL ,
GBP combinations• More measurements on the zero drift• SEM calibration and comparison with CCC
Conceptual design of the new CCC-1
Some boundary conditions• Limited space available in the beam line for running and more importantly for any
repair works once installed.
• Horizontal design – More stable and compact compared to the vertical solution
• All the components in the system should be as reachable as possible for any dismantling/repair works and following cleaning up.
• The system should as independent from the beam line as possible – CCC should not influence beam/other experiments nearby.
• All installation locations may not be accessible when beam line is in operation – complete remote operation should be foreseen.
• Any thermal fluctuation/ pressure difference in the cryostat will affect the SQUID measurements – Hence the system should be as “quiet” as possible.
Conceptual design of the new CCC-2
• Isolation vacuum• Disturbing the accelerator vacuum – consequences : CCC is
like a cryo-pump when cold -- During warming up, release of several types of gases condensed on the cold CCC
• Venting and hence any modifications is restricted by the beam line vacuum conditions.
• Constant thermal load by radiation onto the cryostat from the beam tube – long “warm-hole” is unavoidable without isolation vacuum.
• With isolation vacuum, one can do a lot more studies during test measurements (more realistic simulation of beam currents).
LHe liquefaction plants
LHeP18
PT410
GM Based GWR-ATLLiquefaction unit
Challenges with Re-cooling systems
• Purity of the Helium boil-off• Mechanical isolation of the CCC cryostat
from the cryo-cooler• Thermal instabilities causes drastic zero
drifts in the SQUID signal• Installation and operation space
availability in all beam line
New CCC Concept
Mag. shield incl. pickup coil
isolation vacuum chamber
Radiation shield
Cooling- cold helium boil-off
LHe cryostat
Bellow – isolation vacuum
Ceramic spacer
Suspension (3) Mag. shield
Suspension (3) LHe cryostat
Support - Mag. shield
Bellow – LHe cryostat
SQUID signal feedthrough
Vacuum connection
SQUID sensor
1000 mm
657 mm
435 mm
160 mm550 mm
CCC Installed in HTP
Thanks for your attention
Recommended