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

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

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

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

The GOOFIE set-up Features: Problems: Drift field: 400 V/cm (unprecedented) like in the TPC Field Cage Voltage: -10 KV Pickup Voltage: +1500 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".

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

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

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)

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

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.

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 = 2.5238 G = 595 CO2 =10 N2 = 5 * * Fitted planes Simulations

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

Shift measured Vd to pressure at GSI <P>CERN = 0.990 bar <P>GSI = 1.005 bar DP= 0.015 bar DV= 0.3 cm/ms Central points of our simulation: Vd = 2.5238 G = 595 CO2 =10 N2 = 5 Why it is necessary to shift? Only for GSI conditions !!!

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

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)

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

Extra plots T/P projection all data points

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

Extra plots Composition curve -non-shifted values

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

Extra plots Vd versus P –old plots

Extra plots Far Trigger counter connection scheme