PNPI R&D on based detector for MUCH central part (supported by INTAS 06-1000012-8781)

PNPI R&D on based detector for MUCH central part

(supported by INTAS 06-1000012-8781)

E. Chernyshova, V.Evseev, V. Ivanov, A. Khanzadeev, B. Komkov, L. Kudin, V.Nikulin, G. Rybakov, E. Rostchin, V.Samsonov,

O.Tarasenkova, S. Volkov

A.Khanzdeev, March_2009, GSI

Main steps of R&D at present stage:

■ Choosing the working gas

■ Radiation hardness of materials

■ Designing the beam test prototypes


GEM+MICROMEGAS

MICROMEGAS+GEM based tracking detector is considered as candidate for central region.

Pillars made by chemical etching from photo-resistant layer 4mm between pillars, diameter of each pillar - 300μm, height - 75μm

GEM (5x5 cm2) of CERN production

For MICROMEGAS it was used rolled mesh of Russian production

– stainless steel (wire - 32 μm in diameter, cell - 64μm).


Gas gain vs. voltage in the mesh-gem region

Gas gain vs. voltage in the gem-cathode region


Voltage into the drift gaps was always kept - 1500 V/cm

At previous R&D stage we worked with He/CO2 and Ar/CO2 mixtures.

New gas supply system for preparation of 3-component gas mixtures (designed and produced in the end of last year) allowed to study Ar/CO2/iC4H10, He/CO2/iC4H10, Ar/CF4/iC4H10, and He/CF4/iC4H10.


Small addition of isobutane gives huge effect. The same values of gas gain are reached at much lower HV.

Almost twice less energy of discharge for the same value of gas gain

~ 100 Volts


β-source 90Sr (~3∙105 counts/s)

Spark probability was estimated as ratio of spark number (count of the signals laying above some high threshold and detected by the mesh) to number of total counts detected by the anode

The mixture He/CF4/iC4H10 (90/8/2) showed much lower spark probability in comparing to 2-component mixture. Gas gain of 2∙107 is reached at 450 V applied to the mesh and GEM (visible spark problems occurred at 480 V).Current design of FEE supposes gas gain value of 2∙104 which is reached at 300 V. Last point that we tried to measure was at 350 V (gas gain of ~ 2∙105) and during 30 hours we did not detect any sparks (in the picture the last point is result of extrapolation).

For Ar/CF4/iC4H10 (90/8/2) mixture sparks were observed at 380 V

σd=k√x (μm), where x in cm

For 5 mm drift distance σd ≈ 100μm in the best case

A.Khanzdeev, Martch_2009, GSI

Why He and CF4?

Transversal diffusion for He/CF4/iC4H10 almost twice less than for Ar/CF4/iC4H10 or He/CO2/iC4H10

calculations


Using He/CF4/iC4H10 (85/13/2) we can get collection time of ions in the mesh-anode gap plus drift time of electrons passing drift gaps at the level of 100-150 ns

Drawback – number of produced pairs in He based gas mixture is ~4 times less than in Ar − inefficiency

Looks reasonable to try He + Ar (20%, for example)


Ar+ He+

He+10%Ar+He+20%Ar+

Inefficiency

~0.5% ~3.8%

~2% ~1%

полиэтилен 390 кРд

20

30

40

50

60

70

80

4001400240034004400

волновое число,см-1

погл

ощен

ие,%

Каптон

15

25

35

45

4001400240034004400


погл

ощен

ие,%D=390 кРд

D=5,22М Рд

FR-4

15

25

35

45

55

4001400240034004400


погл

ощен

ие,%D=390 кРд

D=5,22МРд

Radiation hardness of construction materials

Co60(E=1.25 MeV) → two expositions of 390 krad and 5.3 Mrad

After irradiation the emitted fractions were detected and analyzed by infrared spectroscopy method

polyethylene FR4kapton

Red – 5.3 Mrad, blue -390 krad

kapton

(polyimid)

noril flan FR4polyethylene

Radiation degradation Coefficient of radiation degradation after dose of 5.3 Mrad


Prices of flan and kapton about 10 times higher than FR4

There is not cupper covered noril,

noril is 2 times more expensive than FR4

Prototype for beam test


Schematics


Prototype chamber elements

Mesh frames

Anod boards

Front-end electronics boards


Anode structure: 2048 pads;

Pad size 1.5x 3 mm2;

Working area 102x109 mm2;

Gap between pads 0.2 mm;

Mask-pad overlap 0.05-0.075 mm;

Through hole diameter 0.5 mm;

Board thickness 1mm


Plans for this year

■ Try He+Ar based gas mixture

■ Measuring the collection time for chosen working gas

■ Building two prototypes (MICROMEGAS+GEM and MICROMEGAS+TGEM) for beam test

■ Preparing electronics for beam test

■ Would be nice to start beam test at PNPI accelerator


Documents

PNPI R&D on based detector for MUCH central part (supported by INTAS 06-1000012-8781)