1. MWPC’s, GEM’s or Micromegas for AD transfer and experimental lines
December 5, 2018
BDI-Day (Kondo GNANVO)

2. BDI-Day (Kondo GNANVO)
Contents
MWPC’s on the AD transfer and experimental lines.
New Gaseous Detectors to replace the MWPC’s.
MWPC, GEM, Micromegas : Performances.
Modification of GEM to replace the MWPC’s
Conclusion
December 5, 2018
BDI-Day (Kondo GNANVO)

3. BDI-Day (Kondo GNANVO)
AD Overview
December 5, 2018
BDI-Day (Kondo GNANVO)

4. AD Experimental Lines Layout
Transfer Line Experimental lines DE1, DE2, DE3, DE4
16 MWPC’s for the extraction and experimental lines.
MWPC’s in a tank with an IN & OUT system
Machine steering
Beam position and size measurements.
MWPC’s perturbs the measurement and destructs the beam
Old chambers and electronics.
Performances limited for high Intensity.
MWPC fragile and maintenance
December 5, 2018
BDI-Day (Kondo GNANVO)

5. Multi Wire Proportional chamber
Limitations of MWPC :
Gain drops at high count rate (intrinsic )
1D detector2 detectors for a 2D profile
Slow response and saturation (intrinsic)
Spatial resolution limited (mechanical)
Wires structure are fragile and subject to aging
AB/BDI/EA
(J. Spanggaard)
2D MWPC
Position from the delay between 2 extremities of a delay line connected to the cathode wire.
December 5, 2018
BDI-Day (Kondo GNANVO)

6. BDI-Day (Kondo GNANVO)
GEM & Micromegas
GEM : Gas Electron Multiplier
Micromegas : Micro Mesh Gaseous Detector
Sauli (CERN EP/GDD 1997)
Copper coated Kapton foil with high density of holes PCB technology
PCB technology Flexibility for Read Out
Giomataris (Saclay 1996)
Metallic Mesh as amplification cathode
PCB technology for Read Out
Both GEM and Micromegas are advanced technology
Detectors already used in some HEP experiments (COMPASS, CAST etc…)
GEM is manufactured at CERN (Sauli)
December 5, 2018
BDI-Day (Kondo GNANVO)

7. BDI-Day (Kondo GNANVO)
GEM Detector
Drift zone
Transfer zone
75 µm µm
Holes density =
Electron microscope view of a GEM foil
December 5, 2018
BDI-Day (Kondo GNANVO)

8. BDI-Day (Kondo GNANVO)
GEM flexible readout
Different 2D Readout
Same PCB technology as GEM
Flexibility for the 2D readout electrodes
Cartesian
Stereo Angle
Pads
2D Cartesian readout
350 µm
400 µm
80 µm
Substrate
Kapton
Copper
COMPASS : equal charge sharing between coordinates
Correlation between charges amplitudes = multiple hits measurements
Good spatial resolution
December 5, 2018
BDI-Day (Kondo GNANVO)

9. BDI-Day (Kondo GNANVO)
Micromegas 2D readout
2D readout
Charge division of the avalanche on the resistive strips Ni-Cr layer (1µm) on Kapton foil (20 µm) glued on epoxy box
Epoxy 400 µm to 1.5 mm (most comonly used)
Glass 10 to 50 µm (Harsh Irradiation condition ?)
Kapton 20 to 5 µm on a Honeycomb structure (Is it possible?).
Strip Substrate
December 5, 2018
BDI-Day (Kondo GNANVO)

10. GEM foil as a preamplification stage
Micromegem : Mesh replaced by a GEM foil => double amplification
GEM + MSGG
Multi GEM
Operation at low voltage
Higher gain
Avoid (reduce) discharge
Reduce charging up effect of the GEM foil
December 5, 2018
BDI-Day (Kondo GNANVO)

11. BDI-Day (Kondo GNANVO)
GEM & Micromegas : Gain
Gain & Discharge probability
GEM
Micromegas
December 5, 2018
BDI-Day (Kondo GNANVO)

12. BDI-Day (Kondo GNANVO)
GEM & Micromegas : Gain
Gain stability
GEM
MWPC, MSGC & Micromegas
December 5, 2018
BDI-Day (Kondo GNANVO)

13. BDI-Day (Kondo GNANVO)
GEM Signal
Electrons
Ions
NO POSITIVE ION TAIL
Very good multi-track resolution
Full Width 20 ns
(for 2 mm gap)
The total length of the detected signal corresponds to the electron drift time in the induction gap:
Double GEM, normal operating conditions (EDRIFT=200 V/cm),
Ion Feedback is ~ 1.5%
December 5, 2018
BDI-Day (Kondo GNANVO)

14. GEM & Micromegas : Spatial resolution
GEM Spatial resolution
Negligible effects (Geometry of the detectors)
GEM X-Y Correlation
Useful for multi track ambiguity resolution
Y position measurement
With resistive strips method
Resolution > 300 µm
Depend on strip Length
December 5, 2018
BDI-Day (Kondo GNANVO)

15. MWPC, GEM & Micromegas Performances
Rate capability
10^4Hz/mm^2
>5x10^5Hz/mm^2
10^6Hz/mm^2
Gain
High 10^6
low 10^3 (single)
> 10^5 (multi GEM)
High > 10^5
Gain stability
Drops at 10^4Hz/mm^2
Stable over 5*10^5Hz/mm^2
Stable over 10^6Hz/mm^2
2D Readout ?
Not really
Yes and flexible
Yes, not flexible
Position resolution
> 200 µm (analog)
50 µm (analog)
Good < 80 µm
Time resolution
~ 100 µs
< 100 ns
Magnetic Field effect
High
Low
Cost
Expensive, fragile
Cheap, robust
December 5, 2018
BDI-Day (Kondo GNANVO)

16. Modification of GEM to replace the MWPC’s
What is available now ?
Modifications of the GEM
Detector geometry to fit the MWPC’s vacuum tank
Drift cathode (Nickel mesh)
Readout connections to fit the MWPC’s electronics
December 5, 2018
BDI-Day (Kondo GNANVO)

17. BDI-Day (Kondo GNANVO)
Conclusion
2D Micro Pattern Gaseous detectors to replace MWPC’s on the AD experimental lines.
GEM detectors and Micromegas are the most promising.
Low cost and high performances.
More accurate beam’s position and beam size measurement.
But not less destructive for the beam.
Different techniques for the beam’s position size measurement
SEM’s, Scintillators, Wire scanners, etc…
They are destructives too !
Not 2D measurement !
Not necessary easy to implement !
For the immediate future
Development of a new GEM detector suitable for the AD MWPC vacuum thank
December 5, 2018
BDI-Day (Kondo GNANVO)

18. BDI-Day (Kondo GNANVO)
END
December 5, 2018
BDI-Day (Kondo GNANVO)