Diego Gonzalez Diaz University of Santiago de CompostelaITEP

IHEP (Protvino), ITEP (Moscow), INR (Moscow), LIP(Coimbra), USC(Santiago de Compostela)

Diego Gonzalez Diaz University of Santiago de Compostela

Diego González Díaz

(Santiago de Compostela-Spain)

A. Blanco, P. Fonte, L. Lopes, R. Ferreira-Marques

(LIP-Coimbra)

Diego Gonzalez Diaz University of Santiago de Compostela

Detector used for tests

- Gas mixture:

80% C2H2F4 + 20% SF6 .

- Normal window glass, 2 mm thick.

- 4-gaps, 0.3 mm thick.

- Aluminum electrodes, 2 mm thick.

- Shielding boxes.

- BGA2712 amplifier.

- Reference BICRON scintillator (110 ps for gammas).

Diego Gonzalez Diaz University of Santiago de Compostela

Sources used for tests

Na22 (~ 0.1 mCi) (mainly used for calibration)Na22 (~ 1 mCi)Co60 (~ 1 mCi)

2222

2222

*

*

NeNe

eNeNa e 2 x 0.511 MeV collinear (positron annihilation)

1.274 MeV

5959

5960

*

*

CoCo

eCoCo e1.173 MeV, 1.332 MeV (opposite directions but not perfectly collinear)

Interaction occurs through Compton scattering in the electrodes. The electron scattered ionizes the gas and is detected. Charge distribution is different than for MIPS.

q

qq ped

eqdq

dN)(

1

Diego Gonzalez Diaz University of Santiago de Compostela

Trigger system used for tests

Efficiency trigger Time resolution trigger

source

20

/12

1

Lx

N

Ldx

dN

L

RPC

self-trigger mode

source

RPC

Coincidence with a 110 ps scintillator

scintillator

Due to the high rate environment, coincidences by chance are dominant and must be suppressed with adecuate cuts.

Diego Gonzalez Diaz University of Santiago de Compostela

)(

)(

TT

1

00

))(

)(()(

T

T

TR

TRT

‘Rate capability’: If the rate capability κ(T) increasesa factor n, the rate can be increased by the samefactor and the performance of the detectorremains unaltered.

oT

TVV *As a first approach, if the

reduced high voltage V* is kept constant

Temperature dependence

deg6

2)(

T

Diego Gonzalez Diaz University of Santiago de Compostela

Time resolution measurements

Time resolution for gammas stands

within 90 ps without significative

dependence on primary rate. So it is

hard to get the κ(T) factor from

timing

measurements.

No signific

ative dependence

[!]

Diego Gonzalez Diaz University of Santiago de Compostela

Efficiency measurements

Na22

Na22 + Co60

Na22 + Co60

(2.5 cm further)

Diego Gonzalez Diaz University of Santiago de Compostela

Efficiency measurements

1

00

))(

)(()(

T

T

TR

TRT

X12

)(Td

e

Increasing T

33 degrees

Diego Gonzalez Diaz University of Santiago de Compostela

Geometric acceptance ≈ 87 %

2

2

/100%5.1

/1007.467

cmHz

cmHzpspsT

Results in Carbon 2GeV/A beam tests, for the same detector. April 2003

Conclusions (I)

T~20 degrees

Diego Gonzalez Diaz University of Santiago de Compostela

2

2

/100)(

%5.1

/100)(

7.467

cmHzTK

cmHzTK

pspsT

When the Temperature increases??

1

00

))(

)(()(

T

T

TR

TRT

Rate capability

deg6

2)(

T

deg9

2)(

T

measured expected Under study!

Conclusions (II)

Diego Gonzalez Diaz University of Santiago de Compostela

Geometric acceptance ≈ 87 %

for κ(T) measured in 30 degrees increase

Conclusions (III)

Diego Gonzalez Diaz University of Santiago de Compostela

App1: Ageing

T increase of 30 degrees