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