Summary of MM meetingat CEA Saclay, 25/26 Jan 2010

Some selected topics

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

Damien Neyret, slide 8

Damien Neyret, slide 8

Sebastien ProcureurSimulation of the spark rate in a Micromegas detector with Geant4

• Geant4 simulation of MM in hadron beams

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

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

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

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

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

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

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

Examples of pulsesSTANDARD RESISTIVE

Esther Ferrer Ribas

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

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

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

R5 spectra

Meeting at CEA Saclay, 25 Jan 2010 Jörg Wotschack, CERN 17

Gain = 5000 10000

S3 (570 V)

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

Two stages mMega

Double mesh (Dmesh) or Gemas options for

Preamplification gap

Gain vs. HV on the mMega and Gem Gain vs. HV on the mMega and Dmesh

Max. gain vs. HV Gem or Dmesh for Fe55 and Alpha

PARIS 25-01-10

09/06/2009 Rui De Oliveira 22

Resistive protections

Rui de oliveira

09/06/2009 Rui De Oliveira 23

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

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

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

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

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

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