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detectors [2013/10/17 10:50]
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detectors [2013/10/17 10:51]
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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 volume of __xxx cm x xxx cm x xxx cm__ and 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. A technical layout of the detector is shown in [[Fig. xxx]]. The detector consists of 16 stacked-parallel plate ion chambers with narrow anode-cathode gaps, placed along the detector’s central axis. 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 volume of __xxx cm x xxx cm x xxx cm__ and 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. A technical layout of the detector is shown in [[Fig. xxx]]. The detector consists of 16 stacked-parallel plate ion chambers with narrow anode-cathode gaps, placed along the detector’s central axis. 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.\\ |
| The principle of operation of the ionization chamber is illustrated in [[Fig. xxx]]. 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 16-channel | The principle of operation of the ionization chamber is illustrated in [[Fig. xxx]]. 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 16-channel |
| [[https://groups.nscl.msu.edu/nscl_library/manuals/caen/MOD.N568B.pdf|CAEN N568B 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]].// | [[https://groups.nscl.msu.edu/nscl_library/manuals/caen/MOD.N568B.pdf|CAEN N568B 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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