C. M

1

HADES _at_ GSI
MDC participating Institutions I GSI, II
LHE/JINR Dubna, III FZ Rossendorf, IV IPN
Orsay
ORSAY plane
GSI plane
C. Müntz (GSI Darmstadt)
2

Tracking with low mass MDCs

• Momentum-Measurement
• Magnet
• supercond. toroid (6 coils)
• 2p in f, 18o lt J lt 85o

• 24 MDC
• Requirements
• High inv. mass resolution
• Maximum acceptance
• Minimize comb. Background
• Construction materials
• no frames 100 efficiency for electrons
• no multiple scattering
• no ageing
• translates in
• track reconstruction with
• 6 stereo angles per plane,
• 22 planes, redundancy
• 33 m3 active area, ca. 27000 cells
• better than 140 mm intrinsic spatial resolution,
  close to 100 efficiency (MIPS)

Publications Optimisation of low-mass drift
chambers for HADES, Nucl. Instr. Methods A 412
(1998) 38 Development of low-mass drift chambers
for the HADES spectrometer, Nucl. Instr. Methods
A 477 (2002) 387 H.Bokemeyer, J.L.Boyard,
V.Chepurnov, S.Chernenko, H.Daues, F.Dohrmann,
W.Enghardt, O.Fateev, C.Garabatos, L.Glonti,
E.Grosse, J.Hehner, T.Hennino,J.Kempter, W.
Koenig, C.Müntz, L.Naumann, A.Petrov, J.Pouthas,
Ph.Rosier, L.Smykov, H.Stelzer, M.Sobiella,
J.Stroth, J.Wüstenfeld, Y.Zanevsky, P.Zumbruch
C. Müntz (GSI Darmstadt)
3

Tracking w/ low mass MDCs
Gross Properties Active areas 0.35 3.2 m2
Gas vol. 15-260 l, flow 10-20 V/day Cell Size
5x5 14x10 mm2 Stereo angles 40, -20,
0,-0,20,-40 deg., kick angle optimized, cathode
wires at 90 deg. Max expected occupancy 30 (8
average)
Materials Sense wire 20mm Au/W Cathode Field
wires 80 mm Al Windows 12 mm Al-mylar Narrow Al
frames, 0.5 t load Operating gas He-iC4H10
60-40 Operating voltages -1.75 -2.3 kV
(cathode, field)
Drift Velocity
El. Field
C. Müntz (GSI Darmstadt)
4

Performance
Firing wires
Layer efficiency gt 98
C. Müntz (GSI Darmstadt)
5

Accelerated Ageing with X-rays (55Fe)
Io 6 nA/cm
C.Garabatos

• Expected charge dose in HADES 10 mC/year/cm
• No measurable gain degradation within an
  equivalent of 2 years running

C. Müntz (GSI Darmstadt)
6

Customized FEE
Daughterboards
ASD8
LVL1-connector
FPC- connector
Motherboard
TDC
FPC

• Analog Read-out
• FPC cable
• Differential amplifier, ASD8 chip, ca. 20/chip
  incl. test, HERA-B
• (F.M.Newcomer, IEEE Trans. Nucl. Sc. NS-40 (4)
  (1993) 630)
• adjustable threshold (one for 16 channels)
• Analog Baord Dubna/GSI, 16 channels (1 fC intr.
  Noise, 30 mW/ch.)

C. Müntz (GSI Darmstadt)
7

Digital Read-out

• TDC Features (8 channels per chip)
• based on semi-customized ASIC
• (NEC, Gleichmann), MAMI-TDC drift chambers
• 700 kDM (design test, incl. 5000 chips)
• Ring oscillator (250/500 ps/ch)
• GSI mode 2 times (t1, t2) multi-hit capable
• Zero spike (t1-t2 lt 20ns) suppression
• Calibration Mode (mixed trigger)
• Measurement of
• Drift time (in common-stop mode)
• Time above threshold (signal shape, charge)
• Efficient Offline noise suppression!

MDC read-out
SAM (GSI)
ROC (GSI)
C. Müntz (GSI Darmstadt)