LB Thesis DAQ Writeup - Revision history

Brenleyt at 16:57, 26 March 2018

2018-03-26T16:57:21Z

Brenleyt at 16:53, 26 March 2018

2018-03-26T16:53:26Z

Brenleyt at 16:52, 26 March 2018

2018-03-26T16:52:24Z

Brenleyt at 16:42, 26 March 2018

2018-03-26T16:42:16Z

Brenleyt at 16:30, 26 March 2018

2018-03-26T16:30:30Z

Brenleyt at 17:45, 12 March 2018

2018-03-12T17:45:41Z

Brenleyt at 17:33, 12 March 2018

2018-03-12T17:33:07Z

Brenleyt at 17:25, 12 March 2018

2018-03-12T17:25:54Z

Brenleyt at 03:55, 12 March 2018

2018-03-12T03:55:51Z

Brenleyt at 00:38, 30 January 2018

2018-01-30T00:38:02Z

← Older revision		Revision as of 16:57, 26 March 2018
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	A wire diagram is shown below:		A wire diagram is shown below:

−	The model of the post amplifier is the ORTEC model 672 Spectroscopy amplifier. The coarse gain was set to 20 and the fine gain was set to 42. The power supply used was an ORTEC 659 5kV Radiation Detector Detector Bias Supply, which was set to 4.5 kV. The model of the ADC used was the Canberra Model 8701,	+	The model of the post amplifier is the ORTEC model 672 Spectroscopy amplifier. The coarse gain was set to 20 and the fine gain was set to 42. The power supply used was an ORTEC 659 5kV Radiation Detector Detector Bias Supply, which was set to 4.5 kV. The model of the ADC used was the Canberra Model 8701, which is a Wilkinson ADC which samples at 100MHz. The integral non-linearity is less than 0.025% over the top 99.5% of the selected range, while the differential non-linearity is less than 0.7% over the top 99.5% of the selected range.

← Older revision		Revision as of 16:53, 26 March 2018
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	Once the pulses have been created within the sensitive volume of the detector and amplified by the pre-amp, they are sent to a post-amp and an ADC with an internal constant fraction discriminator. The amplifier simply further amplifies the signal and the discriminator can be set to reject voltages within a certain range.		Once the pulses have been created within the sensitive volume of the detector and amplified by the pre-amp, they are sent to a post-amp and an ADC with an internal constant fraction discriminator. The amplifier simply further amplifies the signal and the discriminator can be set to reject voltages within a certain range.

−	The ~~HpGe detector~~ uses an internal constant fraction discriminator, which takes an input signal and duplicates it, and scales it by some factor. The duplicated signal is then delayed for some amount of time that is less than the rise time of the signal and a "zero crossing point" is searched for. If the crossing point is found, then a pulse is created, but if no crossing point is found, then the signal is rejected. For the purposes of this experiment the internal CFD was set to reject signals that result is a measurement of 40keV or lower.	+	The analog to digital converter uses an internal constant fraction discriminator, which takes an input signal and duplicates it, and scales it by some factor. The duplicated signal is then delayed for some amount of time that is less than the rise time of the signal and a "zero crossing point" is searched for. If the crossing point is found, then a pulse is created, but if no crossing point is found, then the signal is rejected. For the purposes of this experiment the internal CFD was set to reject signals that result is a measurement of 40keV or lower.

← Older revision		Revision as of 16:52, 26 March 2018
Line 25:		Line 25:
	A wire diagram is shown below:		A wire diagram is shown below:

−	The model of the post amplifier is the ORTEC model 672 Spectroscopy amplifier. The coarse gain was set to 20 and the fine gain was set to 42. The power supply used was an ORTEC 659 5kV Radiation Detector Detector Bias Supply, which was set to 4.5 kV.	+	The model of the post amplifier is the ORTEC model 672 Spectroscopy amplifier. The coarse gain was set to 20 and the fine gain was set to 42. The power supply used was an ORTEC 659 5kV Radiation Detector Detector Bias Supply, which was set to 4.5 kV. The model of the ADC used was the Canberra Model 8701,

← Older revision		Revision as of 16:42, 26 March 2018
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−	Finally the last step is sending the pulse to a peak sensing analog to digital converter (ADC). An analog pulse is created by the detector and when the gate is open, the data acquisition will take place. Assuming the gate is open, the analog pulse is sent through a differentiating circuit, which has an output that is proportional to the rate of change of the signal. Once the circuit finds a maximum, the voltage is held constant and the peak voltage is maintained by a capacitor. If a larger peak appears while the gate is open, the capacitor will charge more to compensate for the larger peak. A comparator is used to check if the analog signals are greater than the previous peak. After the gate closes, the capacitor will discharge ~~through, in older models, a chain of resistors~~. The ~~number of resistors used~~ to ~~drop~~ the voltage ~~to an immeasurable value has~~ a ~~binary value associated with it,~~ which is ~~converted into~~ the ~~channel number. An integrated circuit in resistive mode can also achieve this~~. A wire diagram is shown below:	+	Finally the last step is sending the pulse to a peak sensing analog to digital converter (ADC). An analog pulse is created by the detector and when the gate is open, the data acquisition will take place. Assuming the gate is open, the analog pulse is sent through a differentiating circuit, which has an output that is proportional to the rate of change of the signal. Once the circuit finds a maximum, the voltage is held constant and the peak voltage is maintained by a capacitor. If a larger peak appears while the gate is open, the capacitor will charge more to compensate for the larger peak. A comparator is used to check if the analog signals are greater than the previous peak. After the gate closes, the capacitor will discharge and another gate opens. The gate remains open for as long as the capacitor is discharging. This means that the duration the gate is open is directly proportional to the voltage across the discharging capacitor.This information is assigned a numerical address which is unique to the voltage across the capacitor.
		+
		+
		+	A wire diagram is shown below:

	The model of the post amplifier is the ORTEC model 672 Spectroscopy amplifier. The coarse gain was set to 20 and the fine gain was set to 42. The power supply used was an ORTEC 659 5kV Radiation Detector Detector Bias Supply, which was set to 4.5 kV.		The model of the post amplifier is the ORTEC model 672 Spectroscopy amplifier. The coarse gain was set to 20 and the fine gain was set to 42. The power supply used was an ORTEC 659 5kV Radiation Detector Detector Bias Supply, which was set to 4.5 kV.

@@ Line 3: / Line 3: @@
-The class of detectors used in the photon activation analysis of selenium were high purity germanium detectors. The specific detector used was the GEM40P4 detector from Ortec. This specific detector is cooled with liquid nitrogen to prevent electrons from easily jumping into the conduction band. If the detector is not cooled, then electrons can cross the band gap more easily due to thermal excitations which results in a high level of noise in the detector that will wash out the signal of interest. Once the detector is cold enough, a high voltage can be applied within the detector. For the GEM40P4 detector, the high voltage is set at 4.6kV in a positive bias. After the ionizing radiation passes through the detector, there are 3 main interactions that are of concern. The first interaction is the photoelectric effect. This means that incoming radiation has enough energy to fully liberate an electron creating an electron hole pair. Once the electron hole pair are created within the detector, the electric field created by the applied high voltage will drift the electrons to one terminal and the holes to another which creates a pulse. It should be noted that the size of the pulse is proportional to the energy of the incident photon. This interaction is typically dominant at lower energies.
+The class of detectors used in the photon activation analysis of selenium were high purity germanium detectors. The specific detector used was the GEM40P4 high purity germanium detector from Ortec. This specific detector is cooled with liquid nitrogen to prevent electrons from easily jumping into the conduction band. If the detector is not cooled, then electrons can cross the band gap more easily due to thermal excitations which results in a high level of noise in the detector that will wash out the signal of interest. Once the detector is cold enough, a high voltage can be applied within the detector. For the GEM40P4 detector, the high voltage is set at 4.6kV in a positive bias. After the ionizing radiation passes through the detector, there are 3 main interactions that are of concern. The first interaction is the photoelectric effect. This means that incoming radiation has enough energy to fully liberate an electron creating an electron hole pair. Once the electron hole pair are created within the detector, the electric field created by the applied high voltage will drift the electrons to one terminal and the holes to another which creates a pulse. It should be noted that the size of the pulse is proportional to the energy of the incident photon. This interaction is typically dominant at lower energies.
@@ Line 10: / Line 10: @@
 [Show Picture Of Spectrum]
- A pulse can be created provided that after Compton Scattering multiple times, the photon liberates an electron via the Photoelectric Effect.
+A signal can also be created if a photon Compton Scatters multiple times, then liberates an electron via the Photoelectric Effect
 The final interaction is pair production. If the photon has a high enough energy (1.02 MeV) then the photon can change into an electron positron pair. These can produce pulses within the detector. The size of the pulse is proportional to the energy of the electron and the energy of the positron. The positron can also annihilate within the detector, which can create 511 keV peaks.
-Once the pulses have been created within the sensitive volume of the detector and amplified by the pre-amp, they are sent to a   post-amp and a discriminator. The amplifier simply further amplifies the signal and the discriminator can be set to reject voltages within a certain range.
+Once the pulses have been created within the sensitive volume of the detector and amplified by the pre-amp, they are sent to a   post-amp and an ADC with an internal constant fraction discriminator. The amplifier simply further amplifies the signal and the discriminator can be set to reject voltages within a certain range.
-The GEM detector uses an internal constant fraction discriminator, which takes an input signal and duplicates it, and scales it by some factor. The duplicated signal is then delayed for some amount of time that is less than the rise time of the signal and a "zero crossing point" is searched for. If the crossing point is found, then a pulse is created, but if no crossing point is found, then the signal is rejected. For the purposes of this experiment the internal CFD was set to reject signals that result is a measurement of 40keV or lower.
+The HpGe detector uses an internal constant fraction discriminator, which takes an input signal and duplicates it, and scales it by some factor. The duplicated signal is then delayed for some amount of time that is less than the rise time of the signal and a "zero crossing point" is searched for. If the crossing point is found, then a pulse is created, but if no crossing point is found, then the signal is rejected. For the purposes of this experiment the internal CFD was set to reject signals that result is a measurement of 40keV or lower.

← Older revision		Revision as of 17:45, 12 March 2018
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	Once the pulses have been created within the sensitive volume of the detector and amplified by the pre-amp, they are sent to a post-amp and a discriminator. The amplifier simply further amplifies the signal and the discriminator can be set to reject voltages within a certain range.		Once the pulses have been created within the sensitive volume of the detector and amplified by the pre-amp, they are sent to a post-amp and a discriminator. The amplifier simply further amplifies the signal and the discriminator can be set to reject voltages within a certain range.

−	The GEM detector uses an internal constant fraction discriminator, which	+	The GEM detector uses an internal constant fraction discriminator, which takes an input signal and duplicates it, and scales it by some factor. The duplicated signal is then delayed for some amount of time that is less than the rise time of the signal and a "zero crossing point" is searched for. If the crossing point is found, then a pulse is created, but if no crossing point is found, then the signal is rejected. For the purposes of this experiment the internal CFD was set to reject signals that result is a measurement of 40keV or lower.

← Older revision		Revision as of 17:33, 12 March 2018
Line 16:		Line 16:
	Once the pulses have been created within the sensitive volume of the detector and amplified by the pre-amp, they are sent to a post-amp and a discriminator. The amplifier simply further amplifies the signal and the discriminator can be set to reject voltages within a certain range.		Once the pulses have been created within the sensitive volume of the detector and amplified by the pre-amp, they are sent to a post-amp and a discriminator. The amplifier simply further amplifies the signal and the discriminator can be set to reject voltages within a certain range.

−		+	The GEM detector uses an internal constant fraction discriminator, which
−	~~clear up what which~~ discriminator ~~is being used and what it does~~
−	~~For example~~, ~~if the discriminator is set to reject any pulse that is less than 150 mV, then all signals of that voltage or lower will not be registered by the data acquisition system.~~

← Older revision		Revision as of 17:25, 12 March 2018
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−	Identify models of ~~post-amp,~~ adc~~, and specs for germanium detector~~	+	Identify models of adc

@@ Line 1: / Line 1: @@
 Identify models of post-amp, adc, and specs for germanium detector
 The class of detectors used in the photon activation analysis of selenium were high purity germanium detectors. The specific detector used was the GEM40P4 detector from Ortec. This specific detector is cooled with liquid nitrogen to prevent electrons from easily jumping into the conduction band. If the detector is not cooled, then electrons can cross the band gap more easily due to thermal excitations which results in a high level of noise in the detector that will wash out the signal of interest. Once the detector is cold enough, a high voltage can be applied within the detector. For the GEM40P4 detector, the high voltage is set at 4.6kV in a positive bias. After the ionizing radiation passes through the detector, there are 3 main interactions that are of concern. The first interaction is the photoelectric effect. This means that incoming radiation has enough energy to fully liberate an electron creating an electron hole pair. Once the electron hole pair are created within the detector, the electric field created by the applied high voltage will drift the electrons to one terminal and the holes to another which creates a pulse. It should be noted that the size of the pulse is proportional to the energy of the incident photon. This interaction is typically dominant at lower energies.
@@ Line 19: / Line 21: @@
-Finally the last step is sending the pulse to a peak sensing analog to digital converter (ADC). An analog pulse is created by the detector and when the gate is open, the data acquisition will take place. Assuming the gate is open, the analog pulse is sent through a differentiating circuit, which has an output that is proportional to the rate of change of the signal. Once the circuit finds a maximum, the voltage is held constant and the peak voltage is maintained by a capacitor. If a larger peak appears while the gate is open, the capacitor will charge more to compensate for the larger peak. A comparator is used to check if the analog signals are greater than the previous peak. After the gate closes, the capacitor will discharge through, in older models, a chain of resistors. The number of resistors used to drop the voltage to an immeasurable value has a binary value associated with it, which is converted into the channel number. An integrated circuit in resistive mode can also achieve this.
+Finally the last step is sending the pulse to a peak sensing analog to digital converter (ADC). An analog pulse is created by the detector and when the gate is open, the data acquisition will take place. Assuming the gate is open, the analog pulse is sent through a differentiating circuit, which has an output that is proportional to the rate of change of the signal. Once the circuit finds a maximum, the voltage is held constant and the peak voltage is maintained by a capacitor. If a larger peak appears while the gate is open, the capacitor will charge more to compensate for the larger peak. A comparator is used to check if the analog signals are greater than the previous peak. After the gate closes, the capacitor will discharge through, in older models, a chain of resistors. The number of resistors used to drop the voltage to an immeasurable value has a binary value associated with it, which is converted into the channel number. An integrated circuit in resistive mode can also achieve this. A wire diagram is shown below:

← Older revision		Revision as of 00:38, 30 January 2018
Line 1:		Line 1:
		+	Identify models of post-amp, adc, and specs for germanium detector
		+
	The class of detectors used in the photon activation analysis of selenium were high purity germanium detectors. The specific detector used was the GEM40P4 detector from Ortec. This specific detector is cooled with liquid nitrogen to prevent electrons from easily jumping into the conduction band. If the detector is not cooled, then electrons can cross the band gap more easily due to thermal excitations which results in a high level of noise in the detector that will wash out the signal of interest. Once the detector is cold enough, a high voltage can be applied within the detector. For the GEM40P4 detector, the high voltage is set at 4.6kV in a positive bias. After the ionizing radiation passes through the detector, there are 3 main interactions that are of concern. The first interaction is the photoelectric effect. This means that incoming radiation has enough energy to fully liberate an electron creating an electron hole pair. Once the electron hole pair are created within the detector, the electric field created by the applied high voltage will drift the electrons to one terminal and the holes to another which creates a pulse. It should be noted that the size of the pulse is proportional to the energy of the incident photon. This interaction is typically dominant at lower energies.		The class of detectors used in the photon activation analysis of selenium were high purity germanium detectors. The specific detector used was the GEM40P4 detector from Ortec. This specific detector is cooled with liquid nitrogen to prevent electrons from easily jumping into the conduction band. If the detector is not cooled, then electrons can cross the band gap more easily due to thermal excitations which results in a high level of noise in the detector that will wash out the signal of interest. Once the detector is cold enough, a high voltage can be applied within the detector. For the GEM40P4 detector, the high voltage is set at 4.6kV in a positive bias. After the ionizing radiation passes through the detector, there are 3 main interactions that are of concern. The first interaction is the photoelectric effect. This means that incoming radiation has enough energy to fully liberate an electron creating an electron hole pair. Once the electron hole pair are created within the detector, the electric field created by the applied high voltage will drift the electrons to one terminal and the holes to another which creates a pulse. It should be noted that the size of the pulse is proportional to the energy of the incident photon. This interaction is typically dominant at lower energies.