1. The GOOFIE detector as a Ternary Mixture Monitor
Juan Castillo
GSI
Darmstadt

2. Outline First glance to composition curves The GOOFIE setup
The integrated signal: results in Drift Velocity and Gain
Gas composition calculation
Conclusions

3. TPC gas composition @ CERN
Only a part of the outcome that the GOOFIE is giving us

4. The GOOFIE set-up Gas prOportional For cOunter drIfting Electrons
A Trigger counter
B Trigger counter
C Pickup Detector

5. The GOOFIE set-up Features: Problems:
Drift field: 400 V/cm (unprecedented) like in the TPC
Field Cage Voltage: -10 KV
Pickup Voltage: V
2 cards: one based in the ALTRO chip, one analog NI for reading Temperature and Pressure
Specifications:
d (alpha, counter) = 40 mm (Bragg peak)
drift distance (fixed) = 20.4 cm
Field plates = 30
Installation precision = 20 mm
Problems:
Installation of the alpha sources
New sensor readout electronics -> Driver problems
Detector stability due to a lack of quenching gas (C02)
One ALTRO chip literally "toasted".

6. Events Near and Far Near Event Far Event A_2: Trigger signal
C_2: Pickup signal
Far Event
B_35: Trigger signal
C_35: Pickup signal

7. Integrated signal – 2500 events
Near events: 1363 Far events: 789
Noise events: 348
Info Obtained:
Drift time Td for the drift velocity
( Vd = Ld/Td)
Peak Area for the gain. Integration of both peaks of an integrated signal signal proportional to the gas gain
Fitting function: gamma 4
Fitting windows: dynamic (always 35 bins) (21,56), (166,201) in this case
Noise filter on

8. Correlation between drift velocity and T/P
Values normalized (to see the correlation) using the whole data set
Drift Velocity = Absolute drift velocity values, obtained after a gamma 4 fitting
of each peak of an integrated signal.
(Tnear / P) = T measured by the near sensor divided by measured P (T/P)
(Tfar / P) = T measured by the far sensor divided by measured P (T/P)

9. Correction range (50 data points)
drift velocity correction
Vdc = Vd –p1(T/P - <T/P>)
area (near/far) correction
Ac = A – p1(T/P - <T/P>)
<T/P> = average of all data point (T/P) in the fitting range
p1 = slope of the fitting

10. Absolute and corrected drift velocity
Absolute drift velocity: It is planned to be used as a feedback for the TPC calibration.
Corrected drift velocity: It is used in addition with gain measurements to calculate the gas composition.

11. Vd and Gain dependence on CO2 and N2
Programs used:
Magboltz 7.3
GARFIELD
Simulated data range
CO2 : 9 -11
N2: 4-6 * *
Central points:
Vd =
G = 595
CO2 =10
N2 = 5 * *
Fitted planes
Simulations

12. Analysis Chain –Off-line
Data acquisition
Integrated Signal
(raw values)
Absolute drift velocity
Absolute peak areas
Global T and P values
NI info (T,P,HVF)
ALTRO info
Event files
Merging
Off-line
filter
T/P
correction
Shift of
corrected
values (next slide)
Integrated Signal (corrected values)
Corrected drift velocity
Corrected peak areas
Gas Composition
curves
(CO2, N2)
Normalization
drift velocity and gain
resolution

13. Shift measured Vd to pressure at GSI
<P>CERN = bar
<P>GSI = bar
DP= bar
DV= 0.3 cm/ms
Central points of our simulation:
Vd = G = 595
CO2 = N2 = 5
Why it is
necessary to shift?
Only for
GSI conditions !!!

14. Composition curves Remarks: values shifted to GSI average
gain normalized to the first measured value
drift velocity normalized with the central value
<CO2> = 9.84 ± 0.02
<N2> = 5.42 ± 0.08

15. Conclusions The measured gas composition was
CO2 = 9.8, N2= 5.4, stable during this period.
TO do: on-line analysis, integration into DCS, HV protection
The Goofie has been successfully analyzing the TPC gas
during commissioning period for almost 7 days
Absolute drift velocity measurements in agreement with Laser results (Jens)

16. Backup

17. Extra plots
T/P clouds (2D) ALL data points

18. Extra plots
T/P projection all data points

19. Analysis Chain – On-line (actual status)
T/P correction
(50 data points)
Absolute drift velocity Vd
Absolute gain G
Global T over P
Corrected Vd and G
Integrated signal
(2500 events)
Composition
calculation
data point:
Vd, Vd corrected, G,
G corrected, CO2, N2, time
"Quality
control"
ALTRO info
NI info (T,P,HVF)
Graphical
Interface
PVSS-DIMM
server
event

20. Extra plots
Composition curve
-non-shifted values

21. Noisy event NOISE ! Far Event B_35: Trigger signal C_35: Pickup signal
Triggers connected to FC high voltage to reduce E instabilities –
specially visible in the Far Trigger
Far Event
B_35: Trigger signal
C_35: Pickup signal

22. Extra plots
Vd versus P
–old plots

23. Extra plots
Far Trigger
counter
connection
scheme