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A high-precision drift straw tube counter for particle tracking for accelerator and space experiments
Nuclear Instruments and Methods in Physics Research A 409 (1998) 73—74
A high-precision drift straw tube counter for particle tracking for accelerator and space experiments G. DeCataldo, C. Favuzzi, N. Giglietto, M.N. Mazziotta1, A. Raino´, P. Spinelli* Dipartimento di Fisica dell+Universita& di Bari and INFN, sez. di Bari, Via Amendola 173, 70126 Bari, Italy
Abstract We have designed and tested a straw tube detector prototype to investigate the possibility to operate a full-size device in sealed mode with extremely reduced gas leaks in accelerator experiments and astroparticle physics researches in outer space. In order to acheive a high spatial resolution we tested a “cool”-gas-based mixture, namely, argon—carbon dioxide at atmospheric pressure. In our tests, running the straw tube counter in drift mode with properly designed front-end electronics, we obtained a single-tube spatial resolution of the order of 30 lm. ( 1998 Elsevier Science B.V. All rights reserved.
1. Straw tube detector The straw tube detector consists of two layers, each made up of 16 adjacent tubes to form a double layer close pack configuration. The tubes, 20 cm long, have thin Kapton walls (30 lm) internally coated with copper 0.3 lm thick. They are equipped with a tungsten wire of 25 lm thickness. The frontend electronics is mounted on 16 channels cards. The single channel consists of a H.V. decoupling capacitor, preamplifier, amplifier and discriminator. The technical details of the straw tubes have been described in a previous work [1]. In order to measure the spatial resolution, we performed a test with cosmic rays. We have set up a telescope based on two plastic scintillator
* Corresponding author. 1 Presented by M.N. Mazziotta.
counters equipped with two XP2013 photomultipliers. In the middle, the straw module to be tested is inserted and tilted by 90°. With this arrangement we select cosmic rays crossing 16 channels of the module. A coincidence of the two scintillators (trigger) sends a common start to the TDCs (50 ps time resolution). A stop signal is sent to a straw TDC channel by the output of the ECL/NIM translator.
2. Spatial resolution measurement In our tests we operated the tubes at a pressure slightly above 1 atm. We measured the spatial resolution of the straw tubes filled with a gas mixture based on Ar (80%) and CO (20%). The supply 2 voltage was set to 1450 V. The discriminator threshold of the front-end electronic channel was set at 75 mV. This nominally corresponds to a pulse
0168-9002/98/$19.00 ( 1998 Elsevier Science B.V. All rights reserved PII S 0 1 6 8 - 9 0 0 2 ( 9 7 ) 0 1 2 3 8 - 2
I. TRACKING (GAS)
74
G. DeCataldo et al. /Nucl. Instr. and Meth. in Phys. Res. A 409 (1998) 73—74
Fig. 1. Overall spatial resolution as function of the radial distance of the track from the wire using the fitting procedure.
amplitude of about 1 of the one released by a m.i.p. 10 in the straw tubes average gas thickness, namely, the amplitude of the pulse induced by a single ionization electron cluster in our gas mixture. To measure the single straw tubes spatial resolution, we selected particles that hit three tubes belonging to the same straw layer. The drift time residuals distribution of the muons crossing a straw triplets has been fitted with a Gaussian. Assuming a constant drift velocity of about 6.5 cm/ls [2] we obtain a spatial resolution of a single tube of about 30 lm (inclusive of intrinsic resolution, alignment and electronics). In order to determine the spatial resolution as function of drift distance from the wire, we selected triggered muons events with at least three hits in the straw module. The drift times are converted into drift distances by means of the drift velocity evaluated using the “Garfield” code [2]. Since the
drift distance does not provide the horizontal coordinate of the track intersection with the plane containing the tube wire, but the closest approach distance to the wire, we implemented a software procedure to reconstruct the track in a reliable way. After making corrections for the transit time of the pulses, the track with the lowest s2 was selected. In Fig. 1 we report the spatial resolution as function of the radial distance of the track from the wire. It is possible to notice that these results are consistent and even slightly better than similar ones from Ref. [3]. References [1] E. Barbarito et al., Nucl. Instr. and Meth. A 381 (1996) 39. [2] Garfield, A drift-chamber simulation program, CERN W5050. [3] W.W. Ash et al., Nucl. Instr. and Meth. A 261 (1989) 399.
A high-precision drift straw tube counter for particle tracking for accelerator and space experiments G. DeCataldo, C. Favuzzi, N. Giglietto, M.N. Mazziotta1, A. Raino´, P. Spinelli* Dipartimento di Fisica dell+Universita& di Bari and INFN, sez. di Bari, Via Amendola 173, 70126 Bari, Italy
Abstract We have designed and tested a straw tube detector prototype to investigate the possibility to operate a full-size device in sealed mode with extremely reduced gas leaks in accelerator experiments and astroparticle physics researches in outer space. In order to acheive a high spatial resolution we tested a “cool”-gas-based mixture, namely, argon—carbon dioxide at atmospheric pressure. In our tests, running the straw tube counter in drift mode with properly designed front-end electronics, we obtained a single-tube spatial resolution of the order of 30 lm. ( 1998 Elsevier Science B.V. All rights reserved.
1. Straw tube detector The straw tube detector consists of two layers, each made up of 16 adjacent tubes to form a double layer close pack configuration. The tubes, 20 cm long, have thin Kapton walls (30 lm) internally coated with copper 0.3 lm thick. They are equipped with a tungsten wire of 25 lm thickness. The frontend electronics is mounted on 16 channels cards. The single channel consists of a H.V. decoupling capacitor, preamplifier, amplifier and discriminator. The technical details of the straw tubes have been described in a previous work [1]. In order to measure the spatial resolution, we performed a test with cosmic rays. We have set up a telescope based on two plastic scintillator
* Corresponding author. 1 Presented by M.N. Mazziotta.
counters equipped with two XP2013 photomultipliers. In the middle, the straw module to be tested is inserted and tilted by 90°. With this arrangement we select cosmic rays crossing 16 channels of the module. A coincidence of the two scintillators (trigger) sends a common start to the TDCs (50 ps time resolution). A stop signal is sent to a straw TDC channel by the output of the ECL/NIM translator.
2. Spatial resolution measurement In our tests we operated the tubes at a pressure slightly above 1 atm. We measured the spatial resolution of the straw tubes filled with a gas mixture based on Ar (80%) and CO (20%). The supply 2 voltage was set to 1450 V. The discriminator threshold of the front-end electronic channel was set at 75 mV. This nominally corresponds to a pulse
0168-9002/98/$19.00 ( 1998 Elsevier Science B.V. All rights reserved PII S 0 1 6 8 - 9 0 0 2 ( 9 7 ) 0 1 2 3 8 - 2
I. TRACKING (GAS)
74
G. DeCataldo et al. /Nucl. Instr. and Meth. in Phys. Res. A 409 (1998) 73—74
Fig. 1. Overall spatial resolution as function of the radial distance of the track from the wire using the fitting procedure.
amplitude of about 1 of the one released by a m.i.p. 10 in the straw tubes average gas thickness, namely, the amplitude of the pulse induced by a single ionization electron cluster in our gas mixture. To measure the single straw tubes spatial resolution, we selected particles that hit three tubes belonging to the same straw layer. The drift time residuals distribution of the muons crossing a straw triplets has been fitted with a Gaussian. Assuming a constant drift velocity of about 6.5 cm/ls [2] we obtain a spatial resolution of a single tube of about 30 lm (inclusive of intrinsic resolution, alignment and electronics). In order to determine the spatial resolution as function of drift distance from the wire, we selected triggered muons events with at least three hits in the straw module. The drift times are converted into drift distances by means of the drift velocity evaluated using the “Garfield” code [2]. Since the
drift distance does not provide the horizontal coordinate of the track intersection with the plane containing the tube wire, but the closest approach distance to the wire, we implemented a software procedure to reconstruct the track in a reliable way. After making corrections for the transit time of the pulses, the track with the lowest s2 was selected. In Fig. 1 we report the spatial resolution as function of the radial distance of the track from the wire. It is possible to notice that these results are consistent and even slightly better than similar ones from Ref. [3]. References [1] E. Barbarito et al., Nucl. Instr. and Meth. A 381 (1996) 39. [2] Garfield, A drift-chamber simulation program, CERN W5050. [3] W.W. Ash et al., Nucl. Instr. and Meth. A 261 (1989) 399.