- Email: [email protected]
The Zero-Degree Detector system for fragmentation studies
ARTICLE IN PRESS
Nuclear Instruments and Methods in Physics Research A 579 (2007) 443–446 www.elsevier.com/locate/nima
The Zero-Degree Detector system for fragmentation studies J.H. Adams Jr.a,, M.J. Christla, L.W. Howella, E. Kuznetsovb,c a
NASA Marshall Space Flight Center, Huntsville, AL 35812, USA University of Alabama in Huntsville, Huntsville, AL 35899, USA c Moscow State University, Moscow 119992, Russia
b
Available online 10 April 2007
Abstract The measurement of nuclear fragmentation cross-sections requires the detection and identification of individual projectile fragments. If light and heavy fragments are recorded in the same detector, it may be impossible to distinguish the signal from the light fragment. To overcome this problem, we have developed the Zero-degree Detector System (ZDDS). The ZDDS enables the measurement of crosssections for light fragment production by using pixelated detectors to separately measure the signals of each fragment. The system has been used to measure the fragmentation of beams as heavy as Fe at the NASA Space Radiation Laboratory at Brookhaven National Laboratory and the Heavy Ion Medical Accelerator in Chiba, Japan. Published by Elsevier B.V. PACS: 29.40.Gx Keywords: Ion fragments; Cross-section; Heavy-ion collision; Galactic Cosmic Radiation; Radiation transport model
1. Introduction The Galactic Cosmic Radiation (GCR) poses a hazard for crews on long-space missions. The hazard comes mostly from heavy ions with energies between 102 and 104 MeV/ nucleon. This hazard is measured by the dose equivalent [5]. Calculating the dose equivalent requires knowledge of the linear energy transfer (LET) spectrum in the organ of interest. This LET spectrum must be obtained by propagating the external GCR environment through the spacecraft and overlaying tissue using a radiation transport code [6–8]. All these codes require knowledge of the nuclear fragmentation cross-sections for all the cosmic ray nuclei up to Fe incident of any of the nuclei in spacecraft or the human body. These cross sections are predicted by models that must be based on experimental measurements of fragmentation cross-sections using thin targets. Also these transport codes must be validated with the experimental data obtained from thick-target yield measurements. Both kinds of measurements must be made at heavy-ion accelerators. Corresponding author.
E-mail address: [email protected] (J.H. Adams Jr.). 0168-9002/$ - see front matter Published by Elsevier B.V. doi:10.1016/j.nima.2007.04.094
Prior to 2003 both fragmentation and thick target yield experiments were performed using the Modular Solid State Detector (MSSD) [9], but it was found that this method was unable to distinguish light fragments, see Ref. [10]. The Zero-degree Detector System (ZDDS) was developed to identify and measure light fragments. The ZDDS is used in conjunction with the MSSD to increase the angular acceptance and simultaneously measure multiple-light ion fragments around the beam axis. Later it was found that the measurements could be improved by adding two orthogonal silicon strip detectors on the beam axis. These detectors were helpful for distinguishing multiple fragments in the MSSD and separately detecting light ions. This paper reports on the development of the ZDDS system and its pixelated detectors. The properties of the ZDDS are given in Table 1.
2. Concept The ZDDS consists of 512 silicon charge particle telescopes, each consisting of two 1.45 cm2 detector pads on separate detector planes. These telescopes are arranged in a ring surrounding the beam axis. Each fragment will
ARTICLE IN PRESS 444
J.H. Adams Jr. et al. / Nuclear Instruments and Methods in Physics Research A 579 (2007) 443–446
Table 1 ZDDS properties Active area (cm2) On axis opening (cm2) Dead space between detectors (cm) Number of planes Number of pads per layer Pad size (cm2) Detector bias (V) Thickness (mm) One MIP (fC) Signal/noise ratio at 1 MIP Dynamic range (pC) ADC resolution CSA peak time (ms) Readout time (ms) Power (W)
29.75 29.75 10.3 10.3 0.32 2 512 1.45 44 300 3.84 5 8 16 1.6 3.7 19 Fig. 2. Signals are routed through 60 mm aluminum traces that run over the passivated detector surface from the detector pads to the rows of bonding pads at the detector’s edges. Wire bonds connect detector pads with bonding pads of ceramic card.
phosphorous-doped silicon. A square matrix of 64 pads is made on the rectifying contact side of each wafer. This matrix has overall dimensions of 97 97 mm. Common guard rings occupy a space extending out about 1 mm around the matrix. A gap of 0.07 mm separates each detector pad within the matrix. A passivation layer protects the surface of the detector. This layer has small square windows over each pad to give access for an electrical contact to route signals. The opposite (blocking contact) side of the detector has a gold coating to ensure good contact to the silver-filled adhesive that holds it to the card. Fig. 1. Sixty-four pad silicon detector mounted onto ceramic card. The detectors are 300 mm thick. Signals from all 64 pads are routed on two opposite sides over passivated detector surface.
penetrate two detector pads and will be measured twice. This creates a coincidence. So the signals, even from lightly ionizing fragments, cannot be mistaken for noise. It also reduces the error on the dE/dx measurement by 0.707. Each detector plane consists of eight 64-pad pixilated silicon detectors. The detectors are mounted on 890 um thick ceramic cards, as shown in Fig. 1. These cards are plugged into a 2.36 mm thick printed circuit board (Fig. 3). The front-end electronics are mounted on the opposite side of this board. The two planes are oriented so that the silicon detectors face each other. The incident particles pass through a lighttight cover, a printed circuit board and a ceramic card before reaching the detectors. The detector planes are separated by a 5–10 mm air gap. 3. Detector design 3.1. Design of the pixilated silicon detector The detectors are made on the 300 um thick 6 in. polished wafers of high resistance (R45 kO cm) float zone
3.2. Signal routing from detector pads The detector surface is passivated by 3 mm layer of SiO2. Aluminum traces are deposited on top of this passivation. Each trace is used to connect from a detector pad to one wire bonding pad at the edge of the detector. There are 64 bonding pads in rows along opposite edges of the detector. When the detector is mounted, these pads are wirebonded to corresponding pads on the ceramic card. These pads are connected by short traces to pins along the card’s edges (Fig. 2). Because of the small thickness of the passivation, the stray capacitance between the connecting traces and the detector pads, over which they are routed, can cause a crosstalk between channels. To avoid crosstalk, this capacitance is kept small by making the thickness of the passivation as large as possible and width of traces as small as possible. In this design, the electrical resistance of the traces connecting the pads to the pins must be considered. It must be o20 O to avoid introducing too much Johnson noise. The maximum thickness of the aluminum traces made with standard technology is 1.2 mm. The resistance of a 1.2 mm trace in ohms is R ¼ L*220/W, where W is the trace width (mm) and L is trace length (cm). The longest traces are
ARTICLE IN PRESS J.H. Adams Jr. et al. / Nuclear Instruments and Methods in Physics Research A 579 (2007) 443–446
3.7 cm. For these to have a resistance of 20 O, the width must be 41 mm. A trace width of 60 mm was used in the ZDDS detector design, giving p11 O trace resistance and p9.6 pF of stray trace capacitance to other pads crossed by the trace (Fig. 2). The crosstalk between traces and underplaying pads was measured using the front-end electronics and found to be of the order of 0.013% per 1 pF for a signal input range of 0–4 pC. 3.3. Detector card assembly As mentioned above, each detector is mounted on a ceramic card that provides support and electrical connections. Each 3.4500 4.4500 card has gold traces deposited on its surface that connect to the blocking contact side of the detector. Along opposite edges of each card there is a row of 34 pins. Two middle pins of each row connect to the blocking contact. Each of the remaining pins in each row connects to detector pad (Fig. 2). The pins plug into the detector motherboards. Eight silicon detectors forming a plane are plugged into one motherboard so that six detector cards will be located on one level and two cards are raised by 1.0 mm to clear the detector edges and extended parts of the neighbor detector
445
cards. The readout electronics are located on the opposite side of the motherboard (Fig. 3). 4. Readout electronics The readout electronics use the design developed for the Advanced Thin Ionization Calorimeter (ATIC) experiment [1–4]. Each ZDDS plane carries eight silicon detectors with 512 pads. Application-specific integrated circuits (ASICs), CR1.4 chips, were developed for the ATIC experiment [2]. Each ZDDS plane uses 32 CR1.4 chips, each reading 16 pads. CR1.4 chips are configured in five groups and each group consists of either six or seven CR1.4 chips that are connected in daisy chain (Fig. 4). The CR1.4 chips in each group serially shift out analog signal levels onto a common line. Analog information from all detector pads comes serially on five common lines to five 16-bit ADCs located on the Grandmother board (GMB). The GMB design is based on the ATIC design. The GMB also contains transceivers for connection to the ASIC Control Logic Board (ACLB), a calibration pulse generator based on a 16-bit DAC, analog drivers and control logic for distributing of control signals to CR1.4 chips. The analog signals from the common lines are serially digitized and shifted to ACLB. ACLB contains 2 field-programmable gate arrays (FPGAs). One supports the communication protocol with a custom computer interface and provides on-line sparsification of the readout. The Second FPGA generates control signals for the CR1.4 chips, the calibration DAC and the digitization process on the GMB. Additionally the ACLB carries the trigger circuitry which generates the Track/Hold signals that are routed to the CR1.4 chips. This trigger comes from a trigger scintillator in the beam and is delayed so that the Track/Hold signal occurs at the peak of the shaped output signals in the CR-1.4 chips. The readout time of the full system (two layers of the silicon matrix) for one event is 3.5 ms. 5. ZDDS calibration
Fig. 3. A Zero-degree Detector plane built with eight 64-pad silicon detectors surrounding beam axis. The ZDDS system consists of two such planes.
There are three features of the front-end CR1.4 chip that affect the ZDDS performance: (1) temperature drift of the CR1.4 output base line, measured to be 10 ADC counts per
Fig. 4. Functional diagram of one layer of the Zero-degree Detector.
ARTICLE IN PRESS J.H. Adams Jr. et al. / Nuclear Instruments and Methods in Physics Research A 579 (2007) 443–446
446 10000
interactions with targets. The ZDDS instrument is based on 64 pad silicon detectors that uses carefully designed traces on top of the passivation to connect to the interior pads without introducing excessive crosstalk or noise. We have shown that this system solves the problem of identifying even the lightest fragments in the presence of much heavier fragments from the same incident nucleus.
Events per Bin
1000
100
10
1
Acknowledgments
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16
Atomic Number
Fig. 5. A ZDDS dE/dx spectrum from a thick target yield measurement from 800 MeV/nucleon Si nuclei bombarding a CH4 target.
degree C; (2) differential nonlinearity within the high signal range (above 1000 MIP) that exceeds 5% and (3) channelto-channel crosstalk in the CR1.4 chip that was measured to be 0.3–0.4%. This crosstalk causes a drop in the signals from all the channels on the chip by the order of 3–4 MIP for a signal of 1000 MIP in one channel. To correct the temperature drift, the pedestal measurements are taken regularly during each accelerator run. Differential nonlinearity and CR1.4 channels crosstalk influences are eliminated using ZDDS calibration data. For the ZDDS calibration a set of test pulses with different amplitudes was applied sequentially at each channel of the ZDDS through a standard reference calibration probe. 6. Experimental results Fig. 5 shows the quality of data taken with the ZDDS to measure the thick target yield from 800 MeV/nucleon Si on a CH4 target. While neighboring elements are not fully resolved, peaks can be identified in the data for each atomic number. Also the nonlinearity in the CR-1 chip has not been corrected for the data in this figure so the atomic number assignments are slightly displaced from the charge peaks. 7. Conclusions We have presented a design for a large array of twoelement charged particle telescopes to determine the individual atomic numbers of fragments from heavy-ion
The experimental data presented here were obtained as part of a research project with heavy ions at NIRSHIMAC. The authors also wish to thank the staff of HIMAC for their invaluable assistance during the experiment. The authors would also like to acknowledge the Marshall Space Flight Center Director’s Discretionary Fund for supporting the development of the 64-pad detectors under task #0103. The development of the ZDDS and the measurements made with it were supported by the National Aeronautics and Space Administration under WBS Element: 62-101-15-62.
References [1] J.H. Adams, et al., Silicon matrix detector for ATIC, in: Proceedings of the 26th ICRC, vol.5, Salt Lake City, 1999, p. 76. [2] J.H. Adams, et al., The CR-1 chip: custom VLSI circuitry for cosmic rays, in: Proceedings of the 26th ICRC, vol. 5, Salt Lake City, 1999, p. 69. [3] J.P. Wefel for The ATIC Collaboration, in: Proceedings of the 27th International Cosmic Ray Conference, vol. 6, Hamburg, 2001, p. 2111. [4] V.I. Zatsepin, J.H. Adams, H.S. Ahn, et al., Nucl. Instr. and Meth. A 524 (2004) 195. [5] International Commission on Radiation Units and Measurements, Conversion coefficients for use in radiological protection against external radiation, ICRU Report 57, ICRU Publications, Bethesda, MD, 1998. [6] J.W. Wilson, F.F. Badavi, F.A. Cucinotta, J. Shinn, G. Badhwar, R. Silberberg, C.H. Tsao, L.W. Townsend, R. Tripathi, HZETRN: description of a free-space ion and nucleon transport and shielding computer program, NASA Technical Paper 3495, 1995. [7] A. Fasso’, A. Ferrari, J. Ranft, P.R. Sala, FLUKA: a multi-particle transport code, INFN/TC_05/11, SLAC-R-773, CERN-2005-10, 2005. [8] L.W. Townsend, T.M. Miller, T.A. Gabriel, Radiat. Prot. Dosim. 116 (2005) 135. [9] C.J. Zeitlin, K.A. Frankel, W. Gong, L. Heilbronn, E.J. Lampo, R. Leres, J. Miller, W. Schimmerling, Radiat. Meas. 23 (1994) 65. [10] C. Zeitlin, L. Heilbronn, J. Miller, S.E. Rademacher, T. Borak, T.R. Carter, K.A. Frankel, W. Schimmerling, C.E. Stronach, Phys. Rev. C 56 (1997) 388.
Nuclear Instruments and Methods in Physics Research A 579 (2007) 443–446 www.elsevier.com/locate/nima
The Zero-Degree Detector system for fragmentation studies J.H. Adams Jr.a,, M.J. Christla, L.W. Howella, E. Kuznetsovb,c a
NASA Marshall Space Flight Center, Huntsville, AL 35812, USA University of Alabama in Huntsville, Huntsville, AL 35899, USA c Moscow State University, Moscow 119992, Russia
b
Available online 10 April 2007
Abstract The measurement of nuclear fragmentation cross-sections requires the detection and identification of individual projectile fragments. If light and heavy fragments are recorded in the same detector, it may be impossible to distinguish the signal from the light fragment. To overcome this problem, we have developed the Zero-degree Detector System (ZDDS). The ZDDS enables the measurement of crosssections for light fragment production by using pixelated detectors to separately measure the signals of each fragment. The system has been used to measure the fragmentation of beams as heavy as Fe at the NASA Space Radiation Laboratory at Brookhaven National Laboratory and the Heavy Ion Medical Accelerator in Chiba, Japan. Published by Elsevier B.V. PACS: 29.40.Gx Keywords: Ion fragments; Cross-section; Heavy-ion collision; Galactic Cosmic Radiation; Radiation transport model
1. Introduction The Galactic Cosmic Radiation (GCR) poses a hazard for crews on long-space missions. The hazard comes mostly from heavy ions with energies between 102 and 104 MeV/ nucleon. This hazard is measured by the dose equivalent [5]. Calculating the dose equivalent requires knowledge of the linear energy transfer (LET) spectrum in the organ of interest. This LET spectrum must be obtained by propagating the external GCR environment through the spacecraft and overlaying tissue using a radiation transport code [6–8]. All these codes require knowledge of the nuclear fragmentation cross-sections for all the cosmic ray nuclei up to Fe incident of any of the nuclei in spacecraft or the human body. These cross sections are predicted by models that must be based on experimental measurements of fragmentation cross-sections using thin targets. Also these transport codes must be validated with the experimental data obtained from thick-target yield measurements. Both kinds of measurements must be made at heavy-ion accelerators. Corresponding author.
E-mail address: [email protected] (J.H. Adams Jr.). 0168-9002/$ - see front matter Published by Elsevier B.V. doi:10.1016/j.nima.2007.04.094
Prior to 2003 both fragmentation and thick target yield experiments were performed using the Modular Solid State Detector (MSSD) [9], but it was found that this method was unable to distinguish light fragments, see Ref. [10]. The Zero-degree Detector System (ZDDS) was developed to identify and measure light fragments. The ZDDS is used in conjunction with the MSSD to increase the angular acceptance and simultaneously measure multiple-light ion fragments around the beam axis. Later it was found that the measurements could be improved by adding two orthogonal silicon strip detectors on the beam axis. These detectors were helpful for distinguishing multiple fragments in the MSSD and separately detecting light ions. This paper reports on the development of the ZDDS system and its pixelated detectors. The properties of the ZDDS are given in Table 1.
2. Concept The ZDDS consists of 512 silicon charge particle telescopes, each consisting of two 1.45 cm2 detector pads on separate detector planes. These telescopes are arranged in a ring surrounding the beam axis. Each fragment will
ARTICLE IN PRESS 444
J.H. Adams Jr. et al. / Nuclear Instruments and Methods in Physics Research A 579 (2007) 443–446
Table 1 ZDDS properties Active area (cm2) On axis opening (cm2) Dead space between detectors (cm) Number of planes Number of pads per layer Pad size (cm2) Detector bias (V) Thickness (mm) One MIP (fC) Signal/noise ratio at 1 MIP Dynamic range (pC) ADC resolution CSA peak time (ms) Readout time (ms) Power (W)
29.75 29.75 10.3 10.3 0.32 2 512 1.45 44 300 3.84 5 8 16 1.6 3.7 19 Fig. 2. Signals are routed through 60 mm aluminum traces that run over the passivated detector surface from the detector pads to the rows of bonding pads at the detector’s edges. Wire bonds connect detector pads with bonding pads of ceramic card.
phosphorous-doped silicon. A square matrix of 64 pads is made on the rectifying contact side of each wafer. This matrix has overall dimensions of 97 97 mm. Common guard rings occupy a space extending out about 1 mm around the matrix. A gap of 0.07 mm separates each detector pad within the matrix. A passivation layer protects the surface of the detector. This layer has small square windows over each pad to give access for an electrical contact to route signals. The opposite (blocking contact) side of the detector has a gold coating to ensure good contact to the silver-filled adhesive that holds it to the card. Fig. 1. Sixty-four pad silicon detector mounted onto ceramic card. The detectors are 300 mm thick. Signals from all 64 pads are routed on two opposite sides over passivated detector surface.
penetrate two detector pads and will be measured twice. This creates a coincidence. So the signals, even from lightly ionizing fragments, cannot be mistaken for noise. It also reduces the error on the dE/dx measurement by 0.707. Each detector plane consists of eight 64-pad pixilated silicon detectors. The detectors are mounted on 890 um thick ceramic cards, as shown in Fig. 1. These cards are plugged into a 2.36 mm thick printed circuit board (Fig. 3). The front-end electronics are mounted on the opposite side of this board. The two planes are oriented so that the silicon detectors face each other. The incident particles pass through a lighttight cover, a printed circuit board and a ceramic card before reaching the detectors. The detector planes are separated by a 5–10 mm air gap. 3. Detector design 3.1. Design of the pixilated silicon detector The detectors are made on the 300 um thick 6 in. polished wafers of high resistance (R45 kO cm) float zone
3.2. Signal routing from detector pads The detector surface is passivated by 3 mm layer of SiO2. Aluminum traces are deposited on top of this passivation. Each trace is used to connect from a detector pad to one wire bonding pad at the edge of the detector. There are 64 bonding pads in rows along opposite edges of the detector. When the detector is mounted, these pads are wirebonded to corresponding pads on the ceramic card. These pads are connected by short traces to pins along the card’s edges (Fig. 2). Because of the small thickness of the passivation, the stray capacitance between the connecting traces and the detector pads, over which they are routed, can cause a crosstalk between channels. To avoid crosstalk, this capacitance is kept small by making the thickness of the passivation as large as possible and width of traces as small as possible. In this design, the electrical resistance of the traces connecting the pads to the pins must be considered. It must be o20 O to avoid introducing too much Johnson noise. The maximum thickness of the aluminum traces made with standard technology is 1.2 mm. The resistance of a 1.2 mm trace in ohms is R ¼ L*220/W, where W is the trace width (mm) and L is trace length (cm). The longest traces are
ARTICLE IN PRESS J.H. Adams Jr. et al. / Nuclear Instruments and Methods in Physics Research A 579 (2007) 443–446
3.7 cm. For these to have a resistance of 20 O, the width must be 41 mm. A trace width of 60 mm was used in the ZDDS detector design, giving p11 O trace resistance and p9.6 pF of stray trace capacitance to other pads crossed by the trace (Fig. 2). The crosstalk between traces and underplaying pads was measured using the front-end electronics and found to be of the order of 0.013% per 1 pF for a signal input range of 0–4 pC. 3.3. Detector card assembly As mentioned above, each detector is mounted on a ceramic card that provides support and electrical connections. Each 3.4500 4.4500 card has gold traces deposited on its surface that connect to the blocking contact side of the detector. Along opposite edges of each card there is a row of 34 pins. Two middle pins of each row connect to the blocking contact. Each of the remaining pins in each row connects to detector pad (Fig. 2). The pins plug into the detector motherboards. Eight silicon detectors forming a plane are plugged into one motherboard so that six detector cards will be located on one level and two cards are raised by 1.0 mm to clear the detector edges and extended parts of the neighbor detector
445
cards. The readout electronics are located on the opposite side of the motherboard (Fig. 3). 4. Readout electronics The readout electronics use the design developed for the Advanced Thin Ionization Calorimeter (ATIC) experiment [1–4]. Each ZDDS plane carries eight silicon detectors with 512 pads. Application-specific integrated circuits (ASICs), CR1.4 chips, were developed for the ATIC experiment [2]. Each ZDDS plane uses 32 CR1.4 chips, each reading 16 pads. CR1.4 chips are configured in five groups and each group consists of either six or seven CR1.4 chips that are connected in daisy chain (Fig. 4). The CR1.4 chips in each group serially shift out analog signal levels onto a common line. Analog information from all detector pads comes serially on five common lines to five 16-bit ADCs located on the Grandmother board (GMB). The GMB design is based on the ATIC design. The GMB also contains transceivers for connection to the ASIC Control Logic Board (ACLB), a calibration pulse generator based on a 16-bit DAC, analog drivers and control logic for distributing of control signals to CR1.4 chips. The analog signals from the common lines are serially digitized and shifted to ACLB. ACLB contains 2 field-programmable gate arrays (FPGAs). One supports the communication protocol with a custom computer interface and provides on-line sparsification of the readout. The Second FPGA generates control signals for the CR1.4 chips, the calibration DAC and the digitization process on the GMB. Additionally the ACLB carries the trigger circuitry which generates the Track/Hold signals that are routed to the CR1.4 chips. This trigger comes from a trigger scintillator in the beam and is delayed so that the Track/Hold signal occurs at the peak of the shaped output signals in the CR-1.4 chips. The readout time of the full system (two layers of the silicon matrix) for one event is 3.5 ms. 5. ZDDS calibration
Fig. 3. A Zero-degree Detector plane built with eight 64-pad silicon detectors surrounding beam axis. The ZDDS system consists of two such planes.
There are three features of the front-end CR1.4 chip that affect the ZDDS performance: (1) temperature drift of the CR1.4 output base line, measured to be 10 ADC counts per
Fig. 4. Functional diagram of one layer of the Zero-degree Detector.
ARTICLE IN PRESS J.H. Adams Jr. et al. / Nuclear Instruments and Methods in Physics Research A 579 (2007) 443–446
446 10000
interactions with targets. The ZDDS instrument is based on 64 pad silicon detectors that uses carefully designed traces on top of the passivation to connect to the interior pads without introducing excessive crosstalk or noise. We have shown that this system solves the problem of identifying even the lightest fragments in the presence of much heavier fragments from the same incident nucleus.
Events per Bin
1000
100
10
1
Acknowledgments
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16
Atomic Number
Fig. 5. A ZDDS dE/dx spectrum from a thick target yield measurement from 800 MeV/nucleon Si nuclei bombarding a CH4 target.
degree C; (2) differential nonlinearity within the high signal range (above 1000 MIP) that exceeds 5% and (3) channelto-channel crosstalk in the CR1.4 chip that was measured to be 0.3–0.4%. This crosstalk causes a drop in the signals from all the channels on the chip by the order of 3–4 MIP for a signal of 1000 MIP in one channel. To correct the temperature drift, the pedestal measurements are taken regularly during each accelerator run. Differential nonlinearity and CR1.4 channels crosstalk influences are eliminated using ZDDS calibration data. For the ZDDS calibration a set of test pulses with different amplitudes was applied sequentially at each channel of the ZDDS through a standard reference calibration probe. 6. Experimental results Fig. 5 shows the quality of data taken with the ZDDS to measure the thick target yield from 800 MeV/nucleon Si on a CH4 target. While neighboring elements are not fully resolved, peaks can be identified in the data for each atomic number. Also the nonlinearity in the CR-1 chip has not been corrected for the data in this figure so the atomic number assignments are slightly displaced from the charge peaks. 7. Conclusions We have presented a design for a large array of twoelement charged particle telescopes to determine the individual atomic numbers of fragments from heavy-ion
The experimental data presented here were obtained as part of a research project with heavy ions at NIRSHIMAC. The authors also wish to thank the staff of HIMAC for their invaluable assistance during the experiment. The authors would also like to acknowledge the Marshall Space Flight Center Director’s Discretionary Fund for supporting the development of the 64-pad detectors under task #0103. The development of the ZDDS and the measurements made with it were supported by the National Aeronautics and Space Administration under WBS Element: 62-101-15-62.
References [1] J.H. Adams, et al., Silicon matrix detector for ATIC, in: Proceedings of the 26th ICRC, vol.5, Salt Lake City, 1999, p. 76. [2] J.H. Adams, et al., The CR-1 chip: custom VLSI circuitry for cosmic rays, in: Proceedings of the 26th ICRC, vol. 5, Salt Lake City, 1999, p. 69. [3] J.P. Wefel for The ATIC Collaboration, in: Proceedings of the 27th International Cosmic Ray Conference, vol. 6, Hamburg, 2001, p. 2111. [4] V.I. Zatsepin, J.H. Adams, H.S. Ahn, et al., Nucl. Instr. and Meth. A 524 (2004) 195. [5] International Commission on Radiation Units and Measurements, Conversion coefficients for use in radiological protection against external radiation, ICRU Report 57, ICRU Publications, Bethesda, MD, 1998. [6] J.W. Wilson, F.F. Badavi, F.A. Cucinotta, J. Shinn, G. Badhwar, R. Silberberg, C.H. Tsao, L.W. Townsend, R. Tripathi, HZETRN: description of a free-space ion and nucleon transport and shielding computer program, NASA Technical Paper 3495, 1995. [7] A. Fasso’, A. Ferrari, J. Ranft, P.R. Sala, FLUKA: a multi-particle transport code, INFN/TC_05/11, SLAC-R-773, CERN-2005-10, 2005. [8] L.W. Townsend, T.M. Miller, T.A. Gabriel, Radiat. Prot. Dosim. 116 (2005) 135. [9] C.J. Zeitlin, K.A. Frankel, W. Gong, L. Heilbronn, E.J. Lampo, R. Leres, J. Miller, W. Schimmerling, Radiat. Meas. 23 (1994) 65. [10] C. Zeitlin, L. Heilbronn, J. Miller, S.E. Rademacher, T. Borak, T.R. Carter, K.A. Frankel, W. Schimmerling, C.E. Stronach, Phys. Rev. C 56 (1997) 388.