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detectors [2017/06/19 18:22]
pereira [Ionization chamber]
detectors [2019/04/09 14:24]
pereira [Cathode Readout Drift Chambers (CRDC)]
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 The standard detection system of the S800 consists of a [[Detectors#​Plastic scintillators|plastic scintillator]] at the [[Stations#​Object Station|object station]]; two tracking detector at the [[Stations#​Intermediate Plane Station|intermediate plane station]] ([[Detectors#​Tracking Parallel Plate Avalanche Counters (TPPAC)|TPPAC]]) and a series of detectors at the [[Stations#​Focal Plane Station|focal plane station]] (see figure below), which include two cathode readout drift chambers ([[Detectors#​Cathode Readout Drift Chambers (CRDC)|CRDC]]) located about 1 m apart; a [[Detectors#​Ionization Chamber|multi-segmented ionization chamber]], a thin [[Detectors#​Plastic scintillators|plastic scintillators]] and a [[Detectors#​Hodoscope|Hodoscope]]. The standard detection system of the S800 consists of a [[Detectors#​Plastic scintillators|plastic scintillator]] at the [[Stations#​Object Station|object station]]; two tracking detector at the [[Stations#​Intermediate Plane Station|intermediate plane station]] ([[Detectors#​Tracking Parallel Plate Avalanche Counters (TPPAC)|TPPAC]]) and a series of detectors at the [[Stations#​Focal Plane Station|focal plane station]] (see figure below), which include two cathode readout drift chambers ([[Detectors#​Cathode Readout Drift Chambers (CRDC)|CRDC]]) located about 1 m apart; a [[Detectors#​Ionization Chamber|multi-segmented ionization chamber]], a thin [[Detectors#​Plastic scintillators|plastic scintillators]] and a [[Detectors#​Hodoscope|Hodoscope]].
  
-{{:​wiki:​s800-fp-detectors.jpg?​650|S800 detector station at the Focal Plane.}}+{{:​wiki:​s800-fp-detectors.jpg?​650|S800 detector station at the Focal Plane (figure taken from K. Meierbachtol PhD thesis, MSU, 2012).}}
  
  
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 ===== Cathode Readout Drift Chambers (CRDC) ===== ===== Cathode Readout Drift Chambers (CRDC) =====
-Two Cathode Readout Drift Chamber (CRDC) are used  to measure the transversal positions and angles in  the [[Stations#​Focal Plane station|focal plane]]. The first detector (CRDC1) is located at the nominal optical focal plane, and it is separated 1 m from the second downstream detector (CRDC2). ​ Each detector has an active depth of 1.5 cm, an active area of 26 cm (non-dispersive direction) x 56 cm (dispersive direction), and [[Gas handling system|it is filled]] with a gas mixture consisting of 80% CF<​sub>​4</​sub>​ and 20% C<​sub>​4</​sub>​H<​sub>​10</​sub>​ at a typical pressure of 40 torr. The [[HV bias#​CRDCs|operating high power]] depends on the charge of the measured nuclei. A schematic view of a CRDC can be seen in the figure below.+Two Cathode Readout Drift Chamber (CRDC) are used  to measure the transversal positions and angles in  the [[Stations#​Focal Plane station|focal plane]]. The first detector (CRDC1) is located at the nominal optical focal plane, and it is separated 1 m from the second downstream detector (CRDC2). ​ Each detector has an active depth of 1.5 cm, an active area of 26 cm (non-dispersive direction) x 56 cm (dispersive direction), and [[Gas handling system|it is filled]] with a gas mixture consisting of 80% CF<​sub>​4</​sub>​ and 20% C<​sub>​4</​sub>​H<​sub>​10</​sub>​ at a typical pressure of 40 torr. The detector frame has a volume of 68 cm (dispersive) x 38 cm (non-dispersive) x 10.3 cm (depth). The [[HV bias#​CRDCs|operating high power]] depends on the charge of the measured nuclei. A schematic view of a CRDC can be seen in the figure below.
  
-{{:​wiki:​crdc-drawing.jpg?​600|Schematic view of the two S800 CRDCs.}}+{{:​wiki:​crdc-drawing.jpg?​600|Schematic view of the two S800 CRDCs (this figure was taken from Yurkon et al., NIM A, 422, 291 (1999) and was adapted by G. W. Hitt in his PhD thesis, MSU 2009).}}
  
  
  
-Each detector consists of two windows mounted on frames, two printed circuit boards (PCB) and an anode frame. Each PCB is made of un-masked G-10, and includes a field shaping foil to ensure a uniform field in the active region of the detector. Two G-10 spacers are laminated to the board on each side. The shaping foils are made of 1.9-mm pitch evaporated aluminum strips perpendicularly oriented to the electric field. The anode frame includes a glued cathode grounding plane, an anode wire running across the field, and a Frisch grid. Cathode pads are located in front of and behind the anode wire. The pads have a pitch of 2.54 mm. The anode frame is sandwiched between the two printed circuit boards with two spacers in between, as shown in the figure below.+Each detector consists of two 12-µm PPTA windows mounted on frames, two printed circuit boards (PCB) and an anode frame. Each PCB is made of un-masked G-10, and includes a field shaping foil (70 µg/​cm<​sup>​2</​sup>​ polypropylene with 0.1 µm of evaporated gold) to ensure a uniform field in the active region of the detector. Two G-10 spacers are laminated to the board on each side. The shaping foils are made of 1.9-mm pitch evaporated aluminum strips perpendicularly oriented to the electric field. The anode frame includes a glued cathode grounding plane, an anode wire running across the field, and a Frisch grid. Cathode pads are located in front of and behind the anode wire. The pads have a pitch of 2.54 mm. The anode frame is sandwiched between the two printed circuit boards with two spacers in between, as shown in the figure below.
  
 {{:​wiki:​crdc-section.jpg?​600|Cross section of a CRDCs.}} {{:​wiki:​crdc-section.jpg?​600|Cross section of a CRDCs.}}
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-{{:​wiki:​crdc-section-drift.jpg?​400 |Principle of operation of a CRDC.}}+{{:​wiki:​crdc-section-drift.jpg?​400 |Principle of operation of a CRDC (figure taken from K. Meierbachtol PhD thesis, MSU, 2012).}}
  
 Both  CRDCs are equipped with digital electronics,​ which consist of seven front-end electronic boards (FEE) designed and developed by the [[http://​www.star.bnl.gov/​|STAR collaboration]] ([[http://​www.bnl.gov/​rhic/​|RHIC]]),​ followed by interface boards connected to a programmable FPGA VME module ({{:​wiki:​Manual_JTEC_XLM72VUM.pdf|XLM72}}) like the one used with the [[Detectors#​Tracking Parallel Plate Avalanche Counters (TPPAC)|TPPACs]] in the intermediate image station. Each FEE includes 32 channels of preamplifier shaper, followed by a switch capacitor array (SCA) and an ADC. The processing of signals is driven by the FPGA module. Each SCA samples the signals after a valid trigger is received and sends the information into the ADC. The digitized ​ data are then stored into the internal memory of the FPGA and read out in block mode. The sampling frequency and number of samples read out are adjustable; typical values are 20 MHz and 8 to 12 samples. The time needed for each sampling is around 16 µs. Thus, the dead time of the electronics is directly proportional to the number of samples read out. The main advantage of the on-detector digitalization technique used with the CRDCs is the reduction of noise by avoiding the transmission of analog signals (448 from the two CRDCs) outside the vacuum chamber, and the possibility to record multi-hit events like in traditional TPC detectors. The schematic diagram of the firmware for the reading of the XLM72V FPGA can be found {{:​wiki:​Crdc5v.pdf|here}}. Both  CRDCs are equipped with digital electronics,​ which consist of seven front-end electronic boards (FEE) designed and developed by the [[http://​www.star.bnl.gov/​|STAR collaboration]] ([[http://​www.bnl.gov/​rhic/​|RHIC]]),​ followed by interface boards connected to a programmable FPGA VME module ({{:​wiki:​Manual_JTEC_XLM72VUM.pdf|XLM72}}) like the one used with the [[Detectors#​Tracking Parallel Plate Avalanche Counters (TPPAC)|TPPACs]] in the intermediate image station. Each FEE includes 32 channels of preamplifier shaper, followed by a switch capacitor array (SCA) and an ADC. The processing of signals is driven by the FPGA module. Each SCA samples the signals after a valid trigger is received and sends the information into the ADC. The digitized ​ data are then stored into the internal memory of the FPGA and read out in block mode. The sampling frequency and number of samples read out are adjustable; typical values are 20 MHz and 8 to 12 samples. The time needed for each sampling is around 16 µs. Thus, the dead time of the electronics is directly proportional to the number of samples read out. The main advantage of the on-detector digitalization technique used with the CRDCs is the reduction of noise by avoiding the transmission of analog signals (448 from the two CRDCs) outside the vacuum chamber, and the possibility to record multi-hit events like in traditional TPC detectors. The schematic diagram of the firmware for the reading of the XLM72V FPGA can be found {{:​wiki:​Crdc5v.pdf|here}}.
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 ===== Ionization chamber ===== ===== Ionization chamber =====
-An ionization chamber downstream of both [[Detectors#​Cathode Readout Drift Chambers (CRDC)|CRDCs]] is used to identify the Z number of the transmitted nuclei from their energy loss. The detector has an active area of __xxx cm x xxx cm__ and a depth of approximately 406 mm (16 inches). It [[Gas handling system||is filled]] with P10 gas (90% argon, 10% methane) at a typical pressure of 300 torr, although this value can be increased up to 600 torr for light nuclei. The detector consists of 16 stacked-parallel plate ion chambers with narrow anode-cathode gaps, placed along the detector’s central axis, perpendicular to the beam direction (see figure). The plates are constructed from 70 mg/​cm<​sup>​2</​sup>​ polypropylene with 0.05 µm of aluminum evaporated on each side. The entrance and exit windows of the chamber are made of 14 mg/​cm<​sup>​2</​sup>​ Mylar with an overlay of Kevlar filaments and epoxy.+An ionization chamber downstream of both [[Detectors#​Cathode Readout Drift Chambers (CRDC)|CRDCs]] is used to identify the Z number of the transmitted nuclei from their energy loss. The detector has an active area of approximately 30 cm x 60 cm and a depth of approximately 406 mm (16 inches). It [[Gas handling system|is filled]] with P10 gas (90% argon, 10% methane) at a typical pressure of 300 torr, although this value can be increased up to 600 torr for light nuclei. The detector consists of 16 stacked-parallel plate ion chambers with narrow anode-cathode gaps, placed along the detector’s central axis, perpendicular to the beam direction (see figure). The plates ​of each of these stacked chambers ​are constructed from 70 µg/​cm<​sup>​2</​sup>​ polypropylene with 0.15 µm of aluminum evaporated on each side. The entrance and exit windows of the chamber are made of 12 mg/​cm<​sup>​2</​sup>​ Mylar with an overlay of Kevlar filaments and epoxy.
 {{:​wiki:​ion-chamber-picture.jpg?​500 |Picture of the S800 ionization chamber with its alternating cathode and anode plates.}} {{:​wiki:​ion-chamber-picture.jpg?​500 |Picture of the S800 ionization chamber with its alternating cathode and anode plates.}}
-The electrons and positive ions liberated by the ionization of the gas along the particle trajectory drift towards the closest ​ anode-cathode pair. The drifting electrons and ions absorb the energy stored in the detector capacity and produce a voltage change of the anodes across the resistor. The main advantages of the anode-cathode configuration is that the electrons and ions are collected on a very short distance (about 1.5 cm), thus reducing pile-up and position dependence of the signals. Moreover, dividing the detector into 16 sections reduces the detector capacitance and consequently its noise. The operating voltage depends on the charge of the measured nuclei (e.g. __xxx for xxx and xxx for xxx__). Each anode is attached to a small preamplifier inside the ion chamber. This significantly reduces the electronic noise, although it involves the venting of the whole chamber whenever a malfunctioning preamplifier needs to be replaced. The electronic signals from the preamplifier are sent into a [[https://​groups.nscl.msu.edu/​nscl_library/​manuals/​caen/​MOD.N568B.pdf|CAEN N568B]] 16-channel shaper/​amplifier with remotely adjustable gains. The output signals feed a [[https://​groups.nscl.msu.edu/​nscl_library/​manuals/​phillips/​7164H.pdf|Phillips 7164H]] ADC. + 
 +The electrons and positive ions liberated by the ionization of the gas along the particle trajectory drift towards the closest ​ anode-cathode pair. The drifting electrons and ions absorb the energy stored in the detector capacity and produce a voltage change of the anodes across the resistor. The main advantages of the anode-cathode configuration is that the electrons and ions are collected on a very short distance (about 1.5 cm), thus reducing pile-up and position dependence of the signals. Moreover, dividing the detector into 16 sections reduces the detector capacitance and consequently its noise. Each anode is attached to a small preamplifier inside the ion chamber. This significantly reduces the electronic noise, although it involves the venting of the whole chamber whenever a malfunctioning preamplifier needs to be replaced. The electronic signals from the preamplifier are sent into a [[https://​groups.nscl.msu.edu/​nscl_library/​manuals/​caen/​MOD.N568B.pdf|CAEN N568B]] 16-channel shaper/​amplifier with remotely adjustable gains. The output signals feed a [[https://​groups.nscl.msu.edu/​nscl_library/​manuals/​phillips/​7164H.pdf|Phillips 7164H]] ADC. 
 The energy-loss resolution of the ionization chamber can be significantly improved after correcting the position and momentum dependences. Elements up to Z=50 can be separated. The energy-loss resolution of the ionization chamber can be significantly improved after correcting the position and momentum dependences. Elements up to Z=50 can be separated.
  
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 ===== Hodoscope ===== ===== Hodoscope =====
-Cs(Na) hodoscope detector located downstream of the [[Detectors#​Plastic scintillators|E1 scintillator]] is used to measure the total kinetic energy of implanted nuclei, allowing the identification of different charge states. An additional use recently tested is the measurement of isomer gamma-rays emitted from implanted nuclei. ​+CsI(Na) hodoscope detector located downstream of the [[Detectors#​Plastic scintillators|E1 scintillator]] is used to measure the total kinetic energy of implanted nuclei, allowing the identification of different charge states. An additional use recently tested is the measurement of isomer gamma-rays emitted from implanted nuclei. ​
  
 The hodoscope is composed ​ 32 sodium-doped cession iodide CsI(Na) scintillating crystals manufactured by [[http://​www.scintitech.com/​|ScintiTech]]. Each crystal is 5.1 cm-thick, has an active area of 7.6 cm x 7.6 cm, and is attached to a photomultiplier ([[https://​www.hamamatsu.com/​jp/​en/​R1307.html|Hamamatsu R1307]]). The photo-cathodes are made of a bi-alkali material with a transmission peak at 420 nm. The 32 crystals are arranged in eight rows of 4 crystals each so as to cover approximately the same solid angle than the [[Detectors#​Cathode Readout Drift Chambers (CRDC)|CRDCs]]. The frontal and lateral sides of each crystal are covered with two 150-µm thick layers of a white Teflon reflective material to provide light shielding between the crystals. The photocathodes are connected to a [[https://​groups.nscl.msu.edu/​nscl_library/​manuals/​caen/​MOD.N568B.pdf|CAEN N568B]] 16-channel shaper/​amplifier,​ followed by a [[https://​groups.nscl.msu.edu/​nscl_library/​manuals/​phillips/​7164H.pdf|Phillips 7164H]] 12-bit ADC. The signals from the crystals are gain-matched to a middle position in the ADC spectra by varying the biases of each photocathode. ​ The hodoscope is composed ​ 32 sodium-doped cession iodide CsI(Na) scintillating crystals manufactured by [[http://​www.scintitech.com/​|ScintiTech]]. Each crystal is 5.1 cm-thick, has an active area of 7.6 cm x 7.6 cm, and is attached to a photomultiplier ([[https://​www.hamamatsu.com/​jp/​en/​R1307.html|Hamamatsu R1307]]). The photo-cathodes are made of a bi-alkali material with a transmission peak at 420 nm. The 32 crystals are arranged in eight rows of 4 crystals each so as to cover approximately the same solid angle than the [[Detectors#​Cathode Readout Drift Chambers (CRDC)|CRDCs]]. The frontal and lateral sides of each crystal are covered with two 150-µm thick layers of a white Teflon reflective material to provide light shielding between the crystals. The photocathodes are connected to a [[https://​groups.nscl.msu.edu/​nscl_library/​manuals/​caen/​MOD.N568B.pdf|CAEN N568B]] 16-channel shaper/​amplifier,​ followed by a [[https://​groups.nscl.msu.edu/​nscl_library/​manuals/​phillips/​7164H.pdf|Phillips 7164H]] 12-bit ADC. The signals from the crystals are gain-matched to a middle position in the ADC spectra by varying the biases of each photocathode. ​
detectors.txt · Last modified: 2019/04/09 14:24 by pereira