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Spatial resolution of thin-walled high-pressure drift tubes
Nuclear Instruments and Methods in Physics Research A 634 (2011) 5–7
Contents lists available at ScienceDirect
Nuclear Instruments and Methods in Physics Research A journal homepage: www.elsevier.com/locate/nima
Spatial resolution of thin-walled high-pressure drift tubes V.I. Davkov a, I. Gregor b, D. Haas c, S.V. Mouraviev d, V.V. Myalkovskiy a, L. Naumann e, V.D. Peshekhonov a,n, C. Rembser f, I.A. Rufanov a, N.A. Russakovich a, P. Senger g, S.Yu. Smirnov h, V.O. Tikhomirov d a
Joint Institute for Nuclear Research (JINR), Dubna, Russia Deutsches Elektronen-Synchrotron (DESY), Hamburg, Germany c Departement de Physique Nucle´aire et Corpusculaire (DPNC), Universite´ de Gene ve, Switzerland d P.N. Lebedev Institute of Physics, Moscow, Russia e Institute of Radiation Physics, Forschungszentrum Dresden-Rossendorf, Germany f European Laboratory for Particle Physics (CERN), Geneva, Switzerland g Gesellschaft f¨ ur Schwerionenforschung (GSI), Darmstadt, Germany h National Research Nuclear University (MEPhI), Moscow, Russia b
a r t i c l e in f o
abstract
Article history: Received 13 August 2010 Received in revised form 20 September 2010 Accepted 11 October 2010 Available online 27 October 2010
A small prototype detector based on high pressure thin-walled tubes (straws) has been developed and its parameters have been studied on a bench at JINR, Dubna, and SPS at CERN. The inner diameter of the straws is 9.53 mm. The pressure of the active gas mixture Ar/CO2 (80/20) was varied from 1 to 5 bar. The best spatial resolution achieved in this pressure range is 40 mm. Both the high efficiency and high rate capability are retained. & 2011 Published by Elsevier B.V.
Keywords: Coordinate detector High pressure Thin-walled drift tube Straw Spatial resolution
1. Introduction
2. High pressure straws
The possibility of using thin-walled drift tubes (straws) under high gas pressures for large planar tracking detectors was shown earlier [1]. Straws manufactured by employing the technology used for the ATLAS TRT and COMPASS straw trackers operate under pressures up to 5 bar with minimum gas losses. The main difference between the detector based on high pressure straws and the one employing straws under normal pressure is in the necessity of using external gas manifolds with individual gas transport lines for each straw. The technology of assembling straws together in a plane should minimize potential difference in the length and/or diameter of the straws. The differences in question are significantly reduced when the straws are reinforced by employing the technique used for the ATLAS TRT straws [2,3]. To study the spatial resolution, a small sized prototype was assembled and tested on a bench at JINR and SPS at CERN. The gas pressure of the mixture Ar/CO2 (80/20) was varied from 1 to 5 bar.
The developed prototype contained two layers of straws reinforced by 115 mm long carbon fiber filaments. The inner diameter of the straws under the pressure of 1 bar was 9.53 mm and the outer diameter was 9.67 mm. The first and second layers consist of 2 and 3 straws, respectively, and the gap between the neighboring straws of each layer is 0.52 mm. The layers were staggered by one straw radius. The straws of the prototype were similar to the straws used for the COMPASS tracker and they were wound by two strips—an external strip of a 12 mm thick aluminized kapton HN50 film and an internal strip made of a 40 mm thick conducting kapton XC-160 film with graphite loading [4]. The anode wire is 30 mm gold plated tungsten. The wire tension is 70 g. The straws are gas-tight owing to the employment of polycarbonate end-plugs containing a central copper crimp tube and a lateral tube for connecting the straw inner volume with an outside gas manifold. Changes in straw diameter due to increase in the absolute pressure of gas filling to 2 and 5 bar are 180 and 300 mm, respectively. The observed elongation is 400 mm/m/bar, which can result in bending of the fixed straws [1]. The reinforcement of a straw by the longitudinal carbon fiber filaments glued onto the straw surface reduced the
n
Corresponding author. Tel.: + 7 496 21 65510; fax: + 7 496 21 65767. E-mail addresses: [email protected], [email protected] (V.D. Peshekhonov). 0168-9002/$ - see front matter & 2011 Published by Elsevier B.V. doi:10.1016/j.nima.2010.10.045
6
V.I. Davkov et al. / Nuclear Instruments and Methods in Physics Research A 634 (2011) 5–7
straw size changes. The elongation of such strengthened straws was about 60 mm/m/bar [1]. Tests for gas tightness were carried out earlier for 1.5 m long straws under a gas pressure of 5 bar. The results of the tests have shown that the gas leak is negligibly small.
3. Spatial resolution The tests of the prototype were carried out on the H6 hadron beam line of the SPS at CERN. The high pressure prototype was located between the sensor pixel planes of the EUDET pixel telescope and was operated together with the granulated straw prototype [5,6]. The telescope contains 6 planes of detectors with a pixel size of 30 30 mm2 and 4 scintillation counters. The sensitive
Fig. 3. Straw efficiency for layers in the prototype along the straw radius (X mm) is 99%. The anode voltage is 3.05 kV and the pressure is 3 bar.
Fig. 1. Layout of the detectors in the H6 beam line of the SPS, showing their orientation and the region where particle tracks are recorded. The granulated straw prototype (SSP, with 4 mm diameter segmented straws) and the high pressure straw prototype (HPP) are located in the centre of the EUDET telescope between the sensor pixel detectors (Si plane) and the scintillation counters (SC).
Fig. 4. Distribution characterizing the spatial resolution (s) of a straw. The anode voltage is 3.05 kV and the gas pressure is 3 bar.
Fig. 2. RT dependence for the straws of different layers of the prototype. The number of the TDC counts with 100 ps time-stamping is displayed as a function of the beam position. The technological gap between adjacent straws of the layers is 0.5 mm. This insensitive zone is seen for the gap between straw nos. 2 and 1. The anode voltage is 3.05 kV and the gas pressure is 3 bar.
size of the telescope was 6 6 mm2 and the track reconstruction accuracy was 3 mm for devices located in the centre of the telescope [7,8]. The detector layout is shown in Fig. 1. The readout system was similar to that used for investigating the prototype of the granulated straw detector with straws 4 mm in diameter [6]. The signals from Front-End Electronics, based on MSD-2 amplifiers, entered the MTDC-64 100 ps time-stamp multichannel time-to-digital converter and further were transferred to Data Acquisition of the EUDET telescope [7]. The trigger signals based on the scintillation counters of the telescope were recorded in one of the MTDC channels and the precise time of the recorded events was determined.
V.I. Davkov et al. / Nuclear Instruments and Methods in Physics Research A 634 (2011) 5–7
7
Fig. 5. Spatial resolution as a function of the anode high voltage under the gas pressure of 3 bar (right panel) and the spatial resolution as a function of the gas pressure (left panel).
The prototype was blown with a gas mixture of Ar/CO2 (80/20) and the absolute pressure of the mixture varied from 1 to 5 bar. The collection time of the ionization electrons (maximum drift time corresponding to tracks passing close to the straw wall) increased in this case from 125 to 285 ns. Fig. 2 shows the RT dependence for two straws of the first layer of the prototype and for one straw of the second layer, located in the sensitive area of EUDET. The anode high voltage was 3.05 kV and the gas mixture pressure was 3 bar. The threshold of discriminators for these three straws was about 4.5 fC. One can see that the beam intensity was not uniform along the straw radius. Namely, the maximum of the beam intensity for straw nos. 2 and 3 was in the centre of the straws and near the cathode region, respectively. The efficiency of these straws along their radius is 99% (Fig. 3). Fig. 4 illustrates the distribution of the residuals between the track of the EUDET pixel detectors and the hit in straw nos. 2 and 3 under the same operating conditions. The r.m.s. width of the narrow Gaussian peak of straw no. 3 is 32 mm. The r.m.s. of straw no. 2 is 43 mm; the main reason for deterioration of the mean resolution can be attributed to a large contribution of the central region of the straw. The spatial resolution as a function of the anode voltage for straw nos. 2 and 3 under the pressure of 3 bar is shown in Fig. 5 (left panel). Deterioration of the spatial resolution is evident as the anode voltage changes from 3.05 to 2.70 kV. The resolution deteriorates down by 25% if the anode voltage changes by approximately 250 V. The right panel in Fig. 5 shows the dependence of spatial resolution on gas pressure. It is seen that under a pressure higher than 2.5 bar it is possible to achieve a spatial resolution better than 40 mm. The spatial resolution as a function of the straw radius for the pressures of 1 and 3 bar is given in Fig. 6. The resolution begins to deteriorate closer to the anode at a distance of 2 and 1 mm at these pressure conditions, respectively. The spatial resolutions uniformly averaged over the distance between a track and the anode wire are 49 and 170 mm under the gas pressures of 3 and 1 bar, respectively. The averaged spatial hit resolution nearest to the anode interval (1 mm long) and for the distant part of the straw radius is 95(330) and 37(130) mm, respectively, for the straw under the pressure of 3(1) bar.
4. Conclusion The possibility of using straws with the absolute pressure of gas filling from 2.5 to 4 bar can be realized for large planar tracking detectors of charged particles. In this case they have the smallest
Fig. 6. Spatial resolution as a function of the straw radius (X mm). Top curve—the gas pressure is 1 bar and the anode voltage is 1.85 kV. Bottom curve—the gas pressure is 3 bar and the anode voltage is 3.05 kV.
radiation thickness in comparison to any other type of tracking detectors. The spatial resolution in this pressure range is 30–40 mm. The small increase of the sensitive time of detectors is a certain drawback. Thus, the collection time of the electrons of primary ionization for the straw of 10 mm diameter increases for the pressure in question by 1.5 and 2 times, respectively. High efficiency and high rate capability are retained in the detectors based on high pressure straws. References [1] V.I. Davkov, K.I. Davkov, V.V. Myalkovskiy, V.D. Peshekhonov, Instrum. Exp. Tech. 51 (6) (2008) 787. [2] E. Abat, et al., Published by Institute of Physics Publishing and SISSA, JINST 3, P02013, 2008. [3] Yu.V. Gusakov, et al., Phys. Part. Nucl. 41 (1) (2010) 1. [4] V.N. Bychkov, N. Dedek, W. Dunnweber, et al., Nucl. Instr. and Meth. Phys. Res.V. 556 (2006) 66. [5] Yu.V. Gusakov, V.I. Davkov, K.I. Davkov, et al., Phys. Part. Nucl. 7 (12) (2010) 132. [6] S.N. Bazylev, K.I. Davkov, I. Gregor, et al., A prototype coordinate detector based on granulated thin-walled drift tubes, Nucl. Instr. and Meth. [7] T. Haas, Nucl. Instr. and Meth. Phys. Res. A 569 (2006) 53. [8] D. Haas, EUDET-Report-2009-03.
Contents lists available at ScienceDirect
Nuclear Instruments and Methods in Physics Research A journal homepage: www.elsevier.com/locate/nima
Spatial resolution of thin-walled high-pressure drift tubes V.I. Davkov a, I. Gregor b, D. Haas c, S.V. Mouraviev d, V.V. Myalkovskiy a, L. Naumann e, V.D. Peshekhonov a,n, C. Rembser f, I.A. Rufanov a, N.A. Russakovich a, P. Senger g, S.Yu. Smirnov h, V.O. Tikhomirov d a
Joint Institute for Nuclear Research (JINR), Dubna, Russia Deutsches Elektronen-Synchrotron (DESY), Hamburg, Germany c Departement de Physique Nucle´aire et Corpusculaire (DPNC), Universite´ de Gene ve, Switzerland d P.N. Lebedev Institute of Physics, Moscow, Russia e Institute of Radiation Physics, Forschungszentrum Dresden-Rossendorf, Germany f European Laboratory for Particle Physics (CERN), Geneva, Switzerland g Gesellschaft f¨ ur Schwerionenforschung (GSI), Darmstadt, Germany h National Research Nuclear University (MEPhI), Moscow, Russia b
a r t i c l e in f o
abstract
Article history: Received 13 August 2010 Received in revised form 20 September 2010 Accepted 11 October 2010 Available online 27 October 2010
A small prototype detector based on high pressure thin-walled tubes (straws) has been developed and its parameters have been studied on a bench at JINR, Dubna, and SPS at CERN. The inner diameter of the straws is 9.53 mm. The pressure of the active gas mixture Ar/CO2 (80/20) was varied from 1 to 5 bar. The best spatial resolution achieved in this pressure range is 40 mm. Both the high efficiency and high rate capability are retained. & 2011 Published by Elsevier B.V.
Keywords: Coordinate detector High pressure Thin-walled drift tube Straw Spatial resolution
1. Introduction
2. High pressure straws
The possibility of using thin-walled drift tubes (straws) under high gas pressures for large planar tracking detectors was shown earlier [1]. Straws manufactured by employing the technology used for the ATLAS TRT and COMPASS straw trackers operate under pressures up to 5 bar with minimum gas losses. The main difference between the detector based on high pressure straws and the one employing straws under normal pressure is in the necessity of using external gas manifolds with individual gas transport lines for each straw. The technology of assembling straws together in a plane should minimize potential difference in the length and/or diameter of the straws. The differences in question are significantly reduced when the straws are reinforced by employing the technique used for the ATLAS TRT straws [2,3]. To study the spatial resolution, a small sized prototype was assembled and tested on a bench at JINR and SPS at CERN. The gas pressure of the mixture Ar/CO2 (80/20) was varied from 1 to 5 bar.
The developed prototype contained two layers of straws reinforced by 115 mm long carbon fiber filaments. The inner diameter of the straws under the pressure of 1 bar was 9.53 mm and the outer diameter was 9.67 mm. The first and second layers consist of 2 and 3 straws, respectively, and the gap between the neighboring straws of each layer is 0.52 mm. The layers were staggered by one straw radius. The straws of the prototype were similar to the straws used for the COMPASS tracker and they were wound by two strips—an external strip of a 12 mm thick aluminized kapton HN50 film and an internal strip made of a 40 mm thick conducting kapton XC-160 film with graphite loading [4]. The anode wire is 30 mm gold plated tungsten. The wire tension is 70 g. The straws are gas-tight owing to the employment of polycarbonate end-plugs containing a central copper crimp tube and a lateral tube for connecting the straw inner volume with an outside gas manifold. Changes in straw diameter due to increase in the absolute pressure of gas filling to 2 and 5 bar are 180 and 300 mm, respectively. The observed elongation is 400 mm/m/bar, which can result in bending of the fixed straws [1]. The reinforcement of a straw by the longitudinal carbon fiber filaments glued onto the straw surface reduced the
n
Corresponding author. Tel.: + 7 496 21 65510; fax: + 7 496 21 65767. E-mail addresses: [email protected], [email protected] (V.D. Peshekhonov). 0168-9002/$ - see front matter & 2011 Published by Elsevier B.V. doi:10.1016/j.nima.2010.10.045
6
V.I. Davkov et al. / Nuclear Instruments and Methods in Physics Research A 634 (2011) 5–7
straw size changes. The elongation of such strengthened straws was about 60 mm/m/bar [1]. Tests for gas tightness were carried out earlier for 1.5 m long straws under a gas pressure of 5 bar. The results of the tests have shown that the gas leak is negligibly small.
3. Spatial resolution The tests of the prototype were carried out on the H6 hadron beam line of the SPS at CERN. The high pressure prototype was located between the sensor pixel planes of the EUDET pixel telescope and was operated together with the granulated straw prototype [5,6]. The telescope contains 6 planes of detectors with a pixel size of 30 30 mm2 and 4 scintillation counters. The sensitive
Fig. 3. Straw efficiency for layers in the prototype along the straw radius (X mm) is 99%. The anode voltage is 3.05 kV and the pressure is 3 bar.
Fig. 1. Layout of the detectors in the H6 beam line of the SPS, showing their orientation and the region where particle tracks are recorded. The granulated straw prototype (SSP, with 4 mm diameter segmented straws) and the high pressure straw prototype (HPP) are located in the centre of the EUDET telescope between the sensor pixel detectors (Si plane) and the scintillation counters (SC).
Fig. 4. Distribution characterizing the spatial resolution (s) of a straw. The anode voltage is 3.05 kV and the gas pressure is 3 bar.
Fig. 2. RT dependence for the straws of different layers of the prototype. The number of the TDC counts with 100 ps time-stamping is displayed as a function of the beam position. The technological gap between adjacent straws of the layers is 0.5 mm. This insensitive zone is seen for the gap between straw nos. 2 and 1. The anode voltage is 3.05 kV and the gas pressure is 3 bar.
size of the telescope was 6 6 mm2 and the track reconstruction accuracy was 3 mm for devices located in the centre of the telescope [7,8]. The detector layout is shown in Fig. 1. The readout system was similar to that used for investigating the prototype of the granulated straw detector with straws 4 mm in diameter [6]. The signals from Front-End Electronics, based on MSD-2 amplifiers, entered the MTDC-64 100 ps time-stamp multichannel time-to-digital converter and further were transferred to Data Acquisition of the EUDET telescope [7]. The trigger signals based on the scintillation counters of the telescope were recorded in one of the MTDC channels and the precise time of the recorded events was determined.
V.I. Davkov et al. / Nuclear Instruments and Methods in Physics Research A 634 (2011) 5–7
7
Fig. 5. Spatial resolution as a function of the anode high voltage under the gas pressure of 3 bar (right panel) and the spatial resolution as a function of the gas pressure (left panel).
The prototype was blown with a gas mixture of Ar/CO2 (80/20) and the absolute pressure of the mixture varied from 1 to 5 bar. The collection time of the ionization electrons (maximum drift time corresponding to tracks passing close to the straw wall) increased in this case from 125 to 285 ns. Fig. 2 shows the RT dependence for two straws of the first layer of the prototype and for one straw of the second layer, located in the sensitive area of EUDET. The anode high voltage was 3.05 kV and the gas mixture pressure was 3 bar. The threshold of discriminators for these three straws was about 4.5 fC. One can see that the beam intensity was not uniform along the straw radius. Namely, the maximum of the beam intensity for straw nos. 2 and 3 was in the centre of the straws and near the cathode region, respectively. The efficiency of these straws along their radius is 99% (Fig. 3). Fig. 4 illustrates the distribution of the residuals between the track of the EUDET pixel detectors and the hit in straw nos. 2 and 3 under the same operating conditions. The r.m.s. width of the narrow Gaussian peak of straw no. 3 is 32 mm. The r.m.s. of straw no. 2 is 43 mm; the main reason for deterioration of the mean resolution can be attributed to a large contribution of the central region of the straw. The spatial resolution as a function of the anode voltage for straw nos. 2 and 3 under the pressure of 3 bar is shown in Fig. 5 (left panel). Deterioration of the spatial resolution is evident as the anode voltage changes from 3.05 to 2.70 kV. The resolution deteriorates down by 25% if the anode voltage changes by approximately 250 V. The right panel in Fig. 5 shows the dependence of spatial resolution on gas pressure. It is seen that under a pressure higher than 2.5 bar it is possible to achieve a spatial resolution better than 40 mm. The spatial resolution as a function of the straw radius for the pressures of 1 and 3 bar is given in Fig. 6. The resolution begins to deteriorate closer to the anode at a distance of 2 and 1 mm at these pressure conditions, respectively. The spatial resolutions uniformly averaged over the distance between a track and the anode wire are 49 and 170 mm under the gas pressures of 3 and 1 bar, respectively. The averaged spatial hit resolution nearest to the anode interval (1 mm long) and for the distant part of the straw radius is 95(330) and 37(130) mm, respectively, for the straw under the pressure of 3(1) bar.
4. Conclusion The possibility of using straws with the absolute pressure of gas filling from 2.5 to 4 bar can be realized for large planar tracking detectors of charged particles. In this case they have the smallest
Fig. 6. Spatial resolution as a function of the straw radius (X mm). Top curve—the gas pressure is 1 bar and the anode voltage is 1.85 kV. Bottom curve—the gas pressure is 3 bar and the anode voltage is 3.05 kV.
radiation thickness in comparison to any other type of tracking detectors. The spatial resolution in this pressure range is 30–40 mm. The small increase of the sensitive time of detectors is a certain drawback. Thus, the collection time of the electrons of primary ionization for the straw of 10 mm diameter increases for the pressure in question by 1.5 and 2 times, respectively. High efficiency and high rate capability are retained in the detectors based on high pressure straws. References [1] V.I. Davkov, K.I. Davkov, V.V. Myalkovskiy, V.D. Peshekhonov, Instrum. Exp. Tech. 51 (6) (2008) 787. [2] E. Abat, et al., Published by Institute of Physics Publishing and SISSA, JINST 3, P02013, 2008. [3] Yu.V. Gusakov, et al., Phys. Part. Nucl. 41 (1) (2010) 1. [4] V.N. Bychkov, N. Dedek, W. Dunnweber, et al., Nucl. Instr. and Meth. Phys. Res.V. 556 (2006) 66. [5] Yu.V. Gusakov, V.I. Davkov, K.I. Davkov, et al., Phys. Part. Nucl. 7 (12) (2010) 132. [6] S.N. Bazylev, K.I. Davkov, I. Gregor, et al., A prototype coordinate detector based on granulated thin-walled drift tubes, Nucl. Instr. and Meth. [7] T. Haas, Nucl. Instr. and Meth. Phys. Res. A 569 (2006) 53. [8] D. Haas, EUDET-Report-2009-03.