1. A GEM-BASED DETECTORS FOR BEAM MONITOR AND NEUTRON FLUXES DIAGNOSTICS
G.Corradi, S.Dabagov, D.Hampai, F.Murtas, M.Pistilli, S. Puddu, D.Tagnani
Laboratori Nazionali di Frascati, INFN
P.Valente
Sezione Roma , INFN
M.Angelone, B.Esposito, D.Marocco, M. Pillon, S.Villari
Frascati, ENEA
Gas Electron Multiplier principia
Construction of a standard triple GEM detector
Triple GEM detector as beam monitor
Monitors for UA9 crystal channeling experiment at SPS
Neutron flux monitor for Tokamak
A compact Time Projection Chamber with GEM
Conclusions
IMAGEM

2. A triple GEM Detector GEM foil
A Gas Electron Multiplier (F.Sauli, NIM A ) is made by 50 m thick kapton foil, copper clad on each side and perforated by an high surface-density of bi-conical channels;
Several triple GEM chambers have been built in Frascati in the LHCb Muon Chamber framework*
70 µm
140 µm
Gain 20
8000
GEM foil
* M.Alfonsi et al., The Triple-GEM detector for the M1R1 muon station at LHCb, N14-182, 2005 IEEE NSS Conference, Puerto Rico

3. GEM Performances  higher efficiency at lower gas gain : 96% in 20 ns
The results of several tests on 10x10 cm2 prototype allowed us to select the Ar/CO2/CF4 with geometry 3/1/2/1 mm
 better time resolution 4.8 ns in respect of Ar/CO2
 higher efficiency at lower gas gain : 96% in 20 ns
Max space resolution O(100 mm)
G.Bencivenni et al., NIM A 518 (2004) 106
Ageing studies on whole detector area 20x24 cm2:
25 kCi 60Co source at 10 MHz/cm2 on 500 cm2
Integrated charge 2.2 C/cm2
P. de Simone et al., IEEE Trans. Nucl. Sci. 52 (2005) 2872
Detector performance recovered with a 15 V shift on HV

4. Where we are working now
Gain and readout functions on separate electrodes
Fast electron charge collected on patterned anode
High rate capability and radiation tolerant
Particle conversion
Gain
Readout
Neutron, X ray
Pixel readout,
Radhard electronics

5. A Standard Triple GEM construction
The detectors described in this talk are built starting form the standard 10x10cm2 produced by CERN :
only one GEM foil has been modified to have central electrodes.
The frame for the G3 foil has been modified for the gas inlet
128 pads 6x12 mm2
128 3x6 mm2
128 3x3 mm2
128 1x1 mm2
x0.5 mm2
… … …
G G G1
The GEM are stretched and a G10 frame is glued on top

6. The FEE board used
The card is based on *Carioca Chip and has been designed and realized
in Frascati by Gianni Corradi ; Total dimension : 3x6 cm2
16 channels for each card: channel density of 1 ch/cm2
Sensitivity of 2-3 fC; LVDS output (25 ns); Radhard;
Extremely modular and usable for GEM applications
All the anode PCB have been
designed with the same connector layout
for a total of 128 channels
* Development of the CARIOCA front-end chip for the LHCb muon detector.
W. Bonivento, et al NIM A491: ,2002

7. The mother board On this mother board HV and LV ground are connected
each other through a 10 KW resistor
CARIOCA readout electronics
Signals path
432 LVDS signals out
Threshold & LV in
HV in
HV filters mV
Threshold calibration
6mV/fC fC 7

8. HV supply for GEM detectors
HVGEM is a new device designed and realized at Frascati specifically for the HV power supply of 3GEM detectors.
G. Corradi, F. Murtas and D.Tagnani
A novel HighVoltage System for a triple GEM detector Reference: NIM A46 128
Controlled via Canbus
All the detectors for beam diagnostic described here have been powered with this new device G3 G2 G1
Cathode (up to 5 KV)
A new version with 7 nano-ammeters,
one for each generator element,
is in construction and ready at beginning 2010
12 V

9. HV Online monitor and control
HVGEM system Console
It gives the possibility to set and control directly the 4 fields
and the total gain of our triple GEM chambers
Labview and PVSS
programs
GEM Voltage
(gain)
Fields
Gap dimension

10. Beam monitors for Frascati Test Beam and UA9 experiment at SPS (CERN)

11. Beam monitor at BTF Frascati
Beam profile at BTF in two configuration : narrow and wide beam
6x12 mm2
10 cm
10 cm
Standard diagnostic with scintillating fibers 11

12. GEM monitor on UA9 Experiment at CERN
GEM monitors
Beam halo scattering
Bending Crystal
Proton beam (200 GeV)
main and channeled beam
SPS tunnel
Proton
beam
pipe
Proton beam pipe
The installation just two months after the collaboration request 12

13. Channeling seen by GEMs at UA9
Counting rate on GEM monitor during the Crystal Angular Scan
MD on August 11th
Channeled Beam
seen by Medipix2
Decrease of beam halo scattering, due to channeling
GEM2 2 KHz signals perfectly correlated with scintillators
GEM1 rate is 20Hz (as expected being upstream of the crystal)

14. … if you need other shapes …

15. LUMI GEM Assembling Seven detectors have been built
Pads : 6 x 24/32 mm2
Seven detectors have been built
pads
induction gap
GEM 3
GEM 2
GEM 1
Cathode
Mother board
Final luminometers with Carioca FEE

16. GEM luminometer mounted on Dafne
Electron
monitor
Positron
Monitor 3 1 4 3 1 2 4
Possible developments for a Luminometer at Super B 2

17. Background monitor Readout every second with VME scalers 28 KHz Only1
Only
Electron Beam
Electron
monitor 2 3
Positron
Monitor
48 KHz 4

18. Neutron Flux Monitor for fusion reactors

19. Neutron flux from fusion plasma
Frascati Neutron Generator
at Enea Frascati :
2.5 (DD) and 14 (DT) MeV p
Ar CO2 CF4
3 mm
Detector divided
in two zone :
UDD 700 mm Polyeth.
5 mm Al.
UDT 2 mm Polyeth.
0.2 mm Al.
UDD
UDT

20. Efficiency vs GEM gain g 700KeV g 1.2 MeV
2.5 MeV Neutron
There is a working region without photon contamination with eff = 10-4
Discriminating
power
14 MeV Neutron
UDD
UDT
g 700KeV
g 1.2 MeV

21. Flux vs time and discrimination
Counts/s DD DT
UDD
UDT
More studies on cathode materials are needed to improve discrimination
Installaed at Frascati Tokamak Upgrade : measurements in progress

22. Calibration and Linearity
Higher neutron flux beam are
needed to measure the real
performance of this monitor
Hits on detector (KHz/cm2)
Other 3 order of magnitude
in neutron flux to be explored
Neutrons on detector(MHz/cm2)

23. 3GEM detector for Xray
A collaboration between CEA ENEA INFN has been started to develop diagnostic for burning plasma with soft Xray. A GEM detector with a cathode maylar window has been installed in Cadarache laboratory
This is an image of the spot produced by the X ray source.
The DAQ is realized with a multipurpose CAEN VME module (FPGA) able to produce also prompt control signals for feedback systems.

24. Compact TPC with GEM readout for high intensity beam and ion beam

25. TPG for beam diagnostic
It’s essentially a small TPC with a 4 cm drift and readout with triple GEM
In this way also high current beam can be monitored in position
box cross section
Particle beam
Triple GEM structure
Without magnetic field
FEE electronics
The material budget crossed by a particle is only two kapton foils (<0.2%X0)
used for the field cage necessary for the drift field uniformity
14 strips with 15 resistors (10 MW) for a total field cage current of 1 mA

26. Assembling the TPG chamber
(M. Pistilli)
5 cm

27. Cosmic rays in free running
5 cm
5cm
For this type of monitor a new layout
has been designed for an active
volume of 5x5x4 cm3
Pad dimension 3x6 mm2
Threshold set at 7 fC
Gas mixture Ar CO2 (70-30)
Triple GEM Gain at about 104
Sub-millimetric precision
A gate of 8ms is open randomly without an external trigger
Threshold set at about 7 fC
Gas mixture Ar CO2 (70-30)
Triple GEM Gain at about 104

28. Low intensity beam Two electrons in 10 ns Top view Last event
Front view
Pad layout
Side view
particles
particles

29. High Intensity beam 4400 e-
The time length of a single bunch was 10 ns
Top view
Side view
z distrib.
# hits
History view

30. Test for beam channeling at CERN
Medipix array
8 columns
16 rows
particles
TPC chamber
GEM
readout
Electrons
drift
Beam

31. A Single Proton through the TPC
From online monitor … no offline analysis !
Side view
Front view
History view
Top view
particle
particle

32. Track reconstruction Residual measured by each pad 8 padsmm Z0
s 100mm
Y coordinate (mm) mm
Residuals along the tracks
100 mm
(z)mm
Y coordinate (mm)
50 mm resolution in track position

33. Chamber calibration 11.31 mm 21.34 mm Beam position with a chamber
displacement of 1 cm
Electron drift (mm)
Electron drift (mm)
21.17 mm
11.43 mm mm
Crystal
Main beam
Channeled beam
TPC
40 m

34. Proton Channeling at CERN testmm
front view
# pad
Channeled beam mm
# pad
top view
# pad
Time(nevt)

35. Future developments

36. Polycapillary for Xray focusing
Generation Kind of optics Sizes: length channel energy
1st Assembled lens made of single capillaries m mm ≤ 10 keV
2nd Monolithic lens made of single capillaries cm mm ≤ 10 keV
3rd Assembled lens made of polycapillaries cm mm ≤ 20 keV
4th Monolihic lens made of polycapillaries cm mm ≤ 50 keV
5th Monolithic integral micro lens cm mm ≤ 100 keV
Frascati Lab
Polycapillary
lens or
half lens
Xray source
G-Lens (by S. Dabagov)
Focusing point correlated with X ray energy

37. X Ray spot with polycapillary
Before
First measurements with
polycapillary and GEM detector
3x6 mm2 pads
After
Policapillary
Lens

38. Conclusions
Several portable detectors based on triple GEM technology have been built in Frascati for several purpose : Luminosity monitor, Neutron flux monitor, Xray monitors, Beam position monitors, …
In all of these sectors they show good performances and confirm good radiation hardness
These R&D are producing a rapid fall-out inside and outside INFN (ENEA, CEA, ISIS, Politecnico di Milano…).
Particular interest inside EFDA for burning plasma diagnos.
Using the polycapillary technology, we proposed a new R&D for Xrays monitor and imaging for high fluxes region (Nuclear Fusion Reactors) in collaboration with ENEA and CEA.

40. “Intelligent” Mother Board
We are working on a Intelligent Mother Board with an FPGA on board
able to count the 128 channel hits and/or measure the time respect
to a trigger (1 ns) ; the data are readable through an Ethernet connection.
Carioca
FEE card
Inputs
LVDS
Digital
Outputs
FPGA
Ethernet LV
Trigger H V f i l t e r
gate
busy
eth
Design done (A.Balla, M.Gatta);
Ready in few weeks
FPGA
usb LV

41. Bhabha Correlation The correlation in phi of bhabha events is clear
time Hz
The correlation in phi of bhabha events is clear
More precise analysis is in progress
time
time
The system is able to measure
the particle impact point with
a precision of 8 mm in theta

42. New system with 4 modules
Recently a new system with 4 modules has
been made for the luminometer power supply.
This system is actually working near the Dafne IP
A detail of 4 HV connectors

43. HVGEM prototype stability
s < 1V
Volts
Daq days
Volts g2
s < 1V
Volts
Daq days
Volts
s < 1V
Volts g3
Daq days
Volts
Good gain stability !

44. Kapton foil with 3 lumi GEM
The construction of this type of detector has required a new GEM
design (same kapton and holes structure but different electrodes shapes )
One GEM foil with the
three annular structure
during the stratching
phase for the prototype
construction

45. Carioca Card Sensitivity
The sensitivity is measured vs two different thresholds
DAC Threshold on power supply
Threshold on Carioca
6mV/fC

46. Carioca Card Sensitivity
Q = 5 fC
width=10 ns
Q = 5 fC
width=20 ns
LVDS 5 ns
LVDS 15 ns
The sensitivity has been measured
injecting a charge between 5 and 20 fC with different width
Q = 5 fC
width=30 ns
LVDS 17 ns