Aging tests of MWPC

REGION	M1R1	M1R3	M2R1
RATE (kHz/cm2) from TDR	460	80	37
INTEGRATED CHARGE (C/cm of wire) in 10 years LHC at G=10**5	5.52	0.96	0.444

How to find integrated charge ?
assuming:

10 years LHC are T=10**8 sec (duty cycle 1/3)
50 e-/gap produced by a m.i.p.
gas gain G=10**5
wire pitch P=0.15 cm
m.i.p. rate depends on region

for example, for M1R3 (mip rate =80,000 Hz/cm2) we find:
Q =(10**8 sec)*50*(1.6*10**-19 C)*(80,000 Hz/cm2)*(10**5)*(0.15 cm)
Q = 0.96 C/cm of wire

Comparison GIF test / LNF X-ray test

	GIF	LNF X-RAY
Chamber area	whole chamber ?	2.5 x 2.5 cm2 of one gap
Total Current in chamber (uA)	250	4
Current density (nA/cm of wire)	25	80
High Voltage (V)	3200	3300
Scale factor in gas gain G=G x 2 each 150 Volt	1	~1.58
Gas gain	10^5	~1.58*10^5
Test duration (days)	?	30
Integrated charge (C/cm of wire)	?	0.2
Rate of Compton e- or X-rays (kHz/cm2)	250/1.6=156	800/3/1.58=169
Scale factor in dE/dX	Compton=1.6	X-rays=3
Equivalent m.i.p. rate(kHz/cm2) at G=10^5	250	800
Duty Cycle	65%	100%
Power dissipated in one gap
Space charge effect

Test duration

How long a test at Maximum current density ?
assuming:

10 years LHC are T=10**8 sec (duty cycle 1/3)
Maximum current density = 100 nA/cm
Duty cycle at Casaccia = 80%
Integrated charge for a 30 day test at CASACCIA = 0.207 C/cm of wire

we find:

REGION	M1R1	M1R3	M2R1
N. of days at CASACCIA equivalent to 10 LHC years at 100 nA/cm of wire	800	139	64
N. of equivalent LHC years for a 30 day test at CASACCIA at 100 nA/cm of wire	0.38	2.2	4.7
At what current density (nA/cm) we should operate to perform a 10 LHC year test in 30 days at CASACCIA ?	2600	450	210

Gas heating due to radiation

Summary of useful numbers

10 years LHC (at 1/3 duty cycle) are 10**8 seconds

one m.i.p. produces 50 ion pairs/gap

10 years LHC (at 1/3 duty cycle) are 10**8 seconds	one m.i.p. produces 50 ion pairs/gap
Nominal gas gain is 10**5	For each +150 V increase in voltage, the gas gain doubles
If G=K*(V^alfa) and G=2G for V=V+150 ---> alfa ~ 14.9 (V=3150 --> 3300)	Gas gain factor between 3200 V and 3300 V : (3300/3200)^14.9 = 1.58
Relation between rate and current density at G=10^5:	Rate (m.i.p.)=100 kHz/cm2 at I=10 nA/cm
Number of ion pairs per m.i.p. = 110/cm (55/gap)	Charge per m.i.p in one gap = 0.88 pC/mip

Aging tests of MWPC

Comparison GIF test / LNF X-ray test

Test duration

Gas heating due to radiation

Summary of useful numbers

C.Forti (9-Oct-2002) Send comments/suggestions to : Carlo.Forti@lnf.infn.it

C.Forti (9-Oct-2002)
Send comments/suggestions to : Carlo.Forti@lnf.infn.it