Summary of MM meeting at CEA Saclay , 25/26 Jan 2010
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Transcript of Summary of MM meeting at CEA Saclay , 25/26 Jan 2010
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Summary of MM meetingat CEA Saclay, 25/26 Jan 2010
Some selected topics
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CLAS12 and CompassDamien Neyret
• H4 (RD51) test beam run in fall 2009 in magnetic field• Discharge studies (10 prototypes, different meshes)
– Resistive layers, GEM foils pre-amplification– Charge spreading
• Preliminary results– compatible with old Compass studies (D. Thers et al.)– very small differences between classic MM and bulk– no impact of magnetic field on discharge rate so far– promising results from MM+GEM detector– further studies to be done: resist and MM+GEM with high and low
intensity hadrons, performances with magnetic field, time resolutions
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Damien Neyret, slide 8
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Damien Neyret, slide 8
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Sebastien ProcureurSimulation of the spark rate in a Micromegas detector with Geant4
• Geant4 simulation of MM in hadron beams
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Spark rate estimate and experiment• Tool will be useful to optimize
detector design• Still some doubts about
reliability of simulation at low energies
Sabstien Procureur
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Shuoxing WuAnalysis on November test beam
• Standard bulk detectors (2 M Ω/☐ )• Resistive Kapton: R3 & R4 (250 M Ω/☐) • Resistive paste: R5 (400K Ω/☐ ) • Resistive strips: R6 (Few tens of k Ω/☐)• Resistive pads: R7 • Segmented one: S1
Y
ResistiveN
on-Resistive
X Y X X
Beam
1 mm 0.25 mm 1 mm
Detectors in test
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Sparking behaviors of R6&S1:
350
360
370
380
390
400
410
420
430
440
1 542 1083162421652706324737884329487054115952Spark number
Mesh voltage/V
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1Mesh current/ua
250
270
290
310
330
350
370
390
410
1 92 183 274 365 456 547 638 729 820 911 1002109311841275136614571548
V
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Spark number
uAS1 mesh vol tageS1 mesh current
eight sparking
six sparking
five sparking
four sparking
three sparking
two sparking
one sparking
S1:R6: 400K Ω/ Resistive strips (paste)
8
Shuoxing Wu
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Detector type Spark rate Spark current /mA
Voltage drop
SLHC2 standard 7*E-5 0.4 5%
R3 2 M Ω/ resistive kapton
9.6*E-6 0.2 2%
R5 250 M Ω/ resistive paste
1.6*E-4 0.1 1.5%
R6 400K Ω/resistive strip
6.4*E-6 0.08 0.5%
R7 tens of K Ω/resistive pad
5.9*E-4 0.35 4.5%
Detector performance at same gas gain (~3000)(preliminary):Shuoxing Wu
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Conclusion and outlook:• Resistive coating is a successful method to reduce the
micromegas spark rate and limit the change in mesh voltage and current.
• Good spatial resolution<100mm can be reached with a resistive strip coating detector of 1mm pitch.
• High efficiency (>98%) can be achieved with resistive strip coating micromegas detector, and efficiency drops less than 4% when increasing the beam intensity from 5KHz to 40KHz .
• The definition of real ‘spark’ needs to be discussed.• R&D and studies will continue inside the MAMMA
collaboration (next beam test in 6 months)
Shuoxing Wu
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Topology of sparks: tests in the laboratory
Esther Ferrer Ribas, Arnaud Giganon, Yannis Giomataris, Fabien Jeanneau
24th-25th January 2010, Spark working Meeting Saclay
Compare in exactly the same conditions (same electronic chain)
Amplitude of the spark (charge released)
Dead time
Esther Ferrer Ribas
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Measuring sparks: The Chain
R15.6 KΩ
MM detector HTmeshR2
5.6 KΩ
C = 470 pF
C = 1.5 pF
ORTEC142BAm241 Oscilloscope
Esther Ferrer Ribas
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Examples of pulsesSTANDARD RESISTIVE
Esther Ferrer Ribas
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Amplitude – charge considerations• Standard case: the whole mesh is completely dechargedQtot= Cdet × Vmesh Cdet = 600 pF, Vmesh = 400 V
Ne = Qtot / qe = 24 × 104pC/ qe ~ 1.5 × 1012
Ne ~ 1.5 × 1012
• With the measured pulses in the resistive case: VPA ~ 8 V , C= 1.5 pF GainPA = 450 mV/pC
Ne ~ 2 × 1010
To be continued
•In a systematic way and with all types of resistive detectors…•Need a lower gain PA to avoid saturation in the standard pulses•It seems that the released charge in a resistive detector is ~1000lower than in a standard one•Dead time probably a high gain as well•Careful analyis of the pulses is needed. Study and understand the different regimes
•<
Esther Ferrer Ribas
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Status of test beam data analysis
… with emphasis on resistive coating studies
Progress and questions
15Meeting at CEA Saclay, 25 Jan 2010 Jörg Wotschack, CERN
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R5 Similar to R3 but with more robust resistive
layer and different technique (Rui’s talk) R ≈ 5 kΩ
Meeting at CEA Saclay, 25 Jan 2010 Jörg Wotschack, CERN 16
PCB
Resistive pasteInsulator
≈ 50 µm
1mm
x 0
.15
mm
pad
Mesh
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R5 spectra
Meeting at CEA Saclay, 25 Jan 2010 Jörg Wotschack, CERN 17
Gain = 5000 10000
S3 (570 V)
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R5: first observations
First measurements of R5 (55Fe source) Sparking starts at HVmesh ≈ 560 V
Large currents (several µA) Large HV drop (100–200 V)
R5 signal ≈2 x S3 signal For comparison: R3 signal ≈ 0.8 x S3 signal Charge resolution much worse than for S3
(and R3); escape peak not well separated
Meeting at CEA Saclay, 25 Jan 2010 Jörg Wotschack, CERN 18
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Two stages mMega
Double mesh (Dmesh) or Gemas options for
Preamplification gap
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Gain vs. HV on the mMega and Gem Gain vs. HV on the mMega and Dmesh
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Max. gain vs. HV Gem or Dmesh for Fe55 and Alpha
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PARIS 25-01-10
09/06/2009 Rui De Oliveira 22
Resistive protections
Rui de oliveira
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09/06/2009 Rui De Oliveira 23
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Structure test 3
09/06/2009 Rui De Oliveira 24
40um kapton >1kv breakdownvoltage
1 mm resistorMore than 1kv breakdownVoltage5Kohms (Omegaply in future)
CopperStrip 0.1mm x 100mm
Pad : 150um x 1.5mm Microvia
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09/06/2009 Rui De Oliveira 25
R1
c2
c3
GND
-500V
c1
Mesh
Strip 0.1mm x 10cmGas 130um
PCB 3mm
c4
C1 : 200pF ? Decoupling capacitor for readoutC2 : in the range of 5pF Parasitic capacitor mesh to stripC3 : in the range of 1.5pF Parasitic capacitor strip to GNDC4 : in the range of 1nF Parasitic capacitor mesh to GNDR1 : 1Mohms ? Resistor to discharge stripR2 : 10 Ohms ? Limiting resistor for spark current
R3 0 ohms
charge
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09/06/2009 Rui De Oliveira 26
R1
c2
c3
GND
-400V
c1
-In normal operation the induced charge will be split between Z1 and Z2-Maximum charge will flow through Z1 if Z1<<Z2 -Z2 = (C2 serial C4)//C3 we forget R1 which is high compared to the capacitors-Z2= C2//C3 because C2 serial C4 is close to C2-C1 min should be 10 x C2//C3 : 10x 6.5pf 65pf min 200pf good choice-to capture the maximum of charge :Z1 should be as low as possible
charge Z1
Z2
c4
0 ohms
R3
Normal operation
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09/06/2009 Rui De Oliveira 27
R1
c2
c3
GND
-500V
c1
-In spark mode the current will be mainly define by C4 and Z1- Z1 at 1Ghz is: ZC1 + R3-C1=200pF 3 Ohms at 1Ghz and 100 Ohms at 10Mhz -Peak current : 500V/13ohms = 39A during a few ns (170 A without R3)
500V/110 =4.5A during 100ns-the average current is in this case around 0.7uA (1.5uA without R3)-Up to 10 lines should be sparking at the same time looking at the currents measured
spark Z1
c4
0 ohms
R3
sparks
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09/06/2009 Rui De Oliveira 28
c2
c3
GND
-400V
c5
signal
c4 0 ohms
c6
-In normal operation the induced charge will be split between C5 and C6(on both sides capacitors are virtually grounded)-C6 is in the range of 0.01pf and C5 0.1pf-R1 should be higher than C5 at any frequency but low enough to keep high rates (5K for test 3)
Strip 0.1mm x 10cmpad
R1
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09/06/2009 Rui De Oliveira 29
c2
c3
GND
-400V
c5
signal
c4 0 ohms
c6
-In case of spark C4 will be discharged through C5 (1k Ohms @ 1Ghz, 100k@10Mhz)It will create a peak current of 500V/1k=0.5 A during a few ns
+500V/100K= 5mA during 100ns (0.1A with R1=5K)the average value is in this case in the range of 3nA (R1=50K) and 10nA (R1 =5K)Here also many pads should be sparking at the same time (up to 4uA measured) (500 pads have an area of 15mm x 15mm)
Strip 0.1mm x 10cmpad
R1