1. Beam Monitors with GEM detectors
Balla, Buonomo, Ciambrone, Corradi, Ferrari, Murtas, Mazzitelli, Quintieri, Tagnani
Laboratori Nazionali di Frascati INFN
Bhabha tracker for Dafne Upgrade
Neutron High Flux monitor
Beam monitor for Beam Test Facility
An R&D project of INFN : IMAGEM

2. Bhabha Tracker Luminometer
At Dafne IP1 (ex KLOE) has been installed the Siddharta experiment.
The runs will be used also for Crab Waist studies (for Super B)
Good luminosity measurements are requested.
3GEM Luminometer
e+ e-  e+ e-

3. 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

4. GEM luminometer mounted on IP
The detectors were displaced 5 mm towards the machine center
Electron
monitor
Positron
Monitor 3
5 mm 1 4 3 1 2 4 2

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

6. During injection
1100 KHz
400 mA
345 KHz

7. Bhabha time correlationx 1 4
Readout multihit TDC
Single event
theta
phi

8. 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

9. Neutron Monitor

10. Neutron flux monitor with triple GEM Experimental Setup at FNG (Enea Frascati)
2.4 MeV (DD)
14 MeV (DT)
from fusion reaction

11. Neutron Monitor n p Event display (1 second time gate)
Polyethylene (2mm)
64 pads 10x6 mm2
38.4 cm2
Alu (0.2 mm) p
Ar CO2 CF4
3 mm
Event display (1 second time gate)
Online neutron flux vs time
neutron source spot light

12. Flux vs time GEM hit frequency NE213 measurements
(KHz)
The nominal neutron flux is
measured with a NE213 placed
about 10 meters far form the gun
GEM hit frequency
NE213 measurements
This is the flux measurement
at the working point of 1110 V
(gain = 300)
The number of hits measured
by the GEM chamber follow
more precisely the flux measured
by the NE213
Beam Stop
time (min)

13. Comparison between GEM and NE213
Neutrons on detector (38 cm2)
GEM Counts (KHz)
22 MHz
5.3 MHz
s = 0.2
s = 0.4
s = 0.3
s = 0.9
Time (min)
Beam Stop
Counts (KHz)

14. Event Display The acquisition gate has reduced
to study the cluster size for each neutron :
Two event displays with few neutrons hitting the chamber
event 114
event 129
cluster size 1.28 pads

15. Photon Background At the working point (Gain 300)
neutron
working
point
working
point
At the working point (Gain 300)
the contamination from photons is practically zero

16. Calibration and Linearity
The efficiency mesurement
are in agreement with MC
prediction = 4.1 x10-4
Hits on detector (KHz/cm2)
A test on FTU
(Frascati Tokamak Upgrade)
is foreseen before the end
of this year.
Higher neutron flux beam are
needed to measure the real
performance o this monitor
Neutrons on detector(MHz/cm2)

17. Small TPG for beam monitor

18. 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
A preliminary
field cage built
for recover the
field distortion

19. Horizontal and Vertical Beam profile
Y position 16 pads 6 mm
X position
4 pads 10 mm
BTF vertical beam profile
sybeam (3.7 mm)
2000 tracks
Yposition (mm)

20. TPG performance
The track is reconstructed using the space time relation
single event with two tracks
sy (208 mm)
residual distribution
Yposition (mm)
Y(pads)
top view (1) (2)
Z(mm)
side view (1)
pads
Z(mm)
side view (2)

21. Electronics developed

22. HV supply for GEM detectors
HVGEM is a new device designed and realized at Frascati specifically for the HV power supply of 3GEM detectors.
All the detector for beam diagnostic has been power up with this new device G3 G2 G1
Cathode (up to 5 KV)
Controlled via Canbus
A Corradi, F. Murtas and D.Tagnani
A novel HighVoltage System for a triple GEM detector Nuclear Inst. and Methods in Physics Research, A
Reference: NIMA46128
15 V

23. 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

24. New 16 channels card
The card has been designed and realized (Gianni Corradi)
Total dimension : 3x6 cm2
Channel density of 1 ch/cm2
Sensitivity of 2-3 fC; LVDS output (25 ns); Radhard;
Extremely modular and usable for other GEM applications
Up to now they have been used on:
The Cylindrical GEM for Kloe Inner tracker prototype
GEM track luminometer
two possibility :
for output connectors
out in
out
PCB

25. Carioca GEM FE board GEM track luminometer for DAFNE Upgrade
New chamber with 128 channels

26. “Intelligent” Mother Board
It has already designed a Mother board 12x12 cm2
for Low and High Voltage distribution and able
to receive directly the signal coming from Carioca Cards 128 ch.
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 readble through an ethernet connection. LV
Trigger
FPGA
Ethernet
FEE card
LVDS
Digital
Outputs
Carioca
Carioca
FEE card
FEE card
Inputs
Carioca
Carioca
Inputs

27. Conclusions
Several detectors based on triple GEM technology have been built in Frascati for several purpose : Bhabha track position, Neutron monitor, Beam monitors, Xray, Gamma ray …
In all of these sectors they show good performances and confirm good radiation hardness
These R&D brought us to develop new HV systems and new front end electronics based on well known chips (ASDQ & Carioca GEM).
Future R&D is foreseen on neutron detection for high fluxes (Nuclear Fusion Reactors) in collaboration with ENEA Frascati Tokamak
New electronics for “on board DAQ” based on FPGA

28. Design for Bhabha Luminometer
4 semi anular detectors with 32 pads each
with a total diameter of 20 cm.
PAD PCB (6 x mm2)
Front side
On the back side the places
for 2 FEE cards
Back side

29. 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

30. Hit molteplicity and timing
Without T0 subtraction Over 32 channels
1.27
11 ns
Molteplicity
12 ns
1.28

31. 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

32. LHCb HVGEM System
On September 2007 a new HV system for LHCb GEM chamber has been built in Frascati and installed at CERN
for a total of 24 HV modules and 24 nano Ammeter .
24 Ammeter modules
on the crate upper side
24 HV modules (7 ch each)
on the crate lower side

33. 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 !