hw:lab:spectrochain:script
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| Both sides previous revision Previous revision Next revision | Previous revision | ||
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hw:lab:spectrochain:script [2009/09/15 07:43] szymon.kulis |
hw:lab:spectrochain:script [2019/03/08 14:08] (current) |
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| Assuming that the further signal processing stages add negligible contribution | Assuming that the further signal processing stages add negligible contribution | ||
| to the overall system noise one can estimate the expected resolution of the spectrometric system in terms of the number of electrons, on the basis of eq. <latex>\ref{eq:enc2}</latex>. | to the overall system noise one can estimate the expected resolution of the spectrometric system in terms of the number of electrons, on the basis of eq. <latex>\ref{eq:enc2}</latex>. | ||
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| ==== Practical realization ==== | ==== Practical realization ==== | ||
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| <latex>Q_{in}=\frac{R_2}{R_1+R_2} C_{test} V_{in}</latex>. | <latex>Q_{in}=\frac{R_2}{R_1+R_2} C_{test} V_{in}</latex>. | ||
| - | All capacitances in the shaper are changeable in a wide range. Such a construction will allow to study the impact of the shaping time value on output signal shape and noise performance of the whole chain. Such a changeable capacitance is realized with tens of binary weight capacitances cross-connected by switches. All switches are controlled by microcontroller. On front panel you may read the shaping time value (<latex> tau=RC </latex>) given in microseconds. To change it you should use the rotary switch (selector). | + | All capacitances in the shaper are changeable in a wide range(mode than two orders of magnitude). Such a construction will allow to study the impact of the shaping time value on output signal shape and noise performance of the whole chain. Such a changeable capacitance are build from tens of binary weight capacitances cross-connected by switches. All switches are controlled by microcontroller. On front panel you may read the shaping time value (<latex> \tau=RC </latex>) given in microseconds. To change it you should use the rotary switch (selector). |
| The outputs of subsequent stages are routed via switches to one output connector. Those switches are controlled by the same digital circuit. The active output is displayed in the box OUTPUT. By clicking rotary knob you can select the active variable: shaping time or output. | The outputs of subsequent stages are routed via switches to one output connector. Those switches are controlled by the same digital circuit. The active output is displayed in the box OUTPUT. By clicking rotary knob you can select the active variable: shaping time or output. | ||
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| ==== Observing the preamplifier output ==== | ==== Observing the preamplifier output ==== | ||
| - | Select 0 as an active output. Try to find output pulse on oscilloscope. Set time base of oscilloscope to 400ns. Does signal look like voltage step? Try to estimate charge gain given by <latex> K_u = \frac{V_{out}}{Q_{in}} </latex> (having in mind formula "charge adapter") and compare it with formula "x". | + | Select 0 as an active output. Try to find output pulse on oscilloscope. Set time base of oscilloscope to 400ns. Does signal look like voltage step? Try to estimate charge gain given by <latex> K_u = \frac{V_{out}}{Q_{in}} </latex> (having in mind formula "charge adapter") and compare it with value given by formula X ref wzmocnienie pream X. |
| Try to look mode deeply on the pulse head (change time base to 40ns). How would you explain the non zero rising time? Then look at the pulse tail. Try to estimate time constant of this pulse and compare it to "y". | Try to look mode deeply on the pulse head (change time base to 40ns). How would you explain the non zero rising time? Then look at the pulse tail. Try to estimate time constant of this pulse and compare it to "y". | ||
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| ==== Linearity check of pre amplifier ==== | ==== Linearity check of pre amplifier ==== | ||
| - | Perform the measurements of output pulse amplitude at the preamplifier output for the set of input test pulse amplitudes. The obtained results write to file ''preamp.dat'' in following format: | + | Perform measurements of pulse amplitude at the preamplifier output for the set of input test pulse amplitudes. The obtained results write to file ''linearity.dat'' in following format: |
| <code> | <code> | ||
| #vin[mv] vout[v] | #vin[mv] vout[v] | ||
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| Look at the first shaper stage output. Check whether the displayed time is equal to the peaking time (time after which pulse reaches its maximum). Look at the pulses at the outputs of subsequent stages. Find their peaking times and see how they are related to the shaping time constant. Try to set the same peaking times for different shaping orders and compare the pulse shapes. | Look at the first shaper stage output. Check whether the displayed time is equal to the peaking time (time after which pulse reaches its maximum). Look at the pulses at the outputs of subsequent stages. Find their peaking times and see how they are related to the shaping time constant. Try to set the same peaking times for different shaping orders and compare the pulse shapes. | ||
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| ==== Noise performance ==== | ==== Noise performance ==== | ||
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| To analyse the measured data use script ''noise.gnu''. See the results in the file ''noise.png''. Are you able to show the optimum shaping time for each filter order ? Does it pay off to use higher shaper orders for noise reduction ? | To analyse the measured data use script ''noise.gnu''. See the results in the file ''noise.png''. Are you able to show the optimum shaping time for each filter order ? Does it pay off to use higher shaper orders for noise reduction ? | ||
| + | ==== Observing pulses from source ==== | ||
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| + | Uda sie zorganizowac zrodlo ? | ||
| ==== Discussions topics==== | ==== Discussions topics==== | ||
| - | * What is main uncertainty source during gain measurements in such setup? | + | * What is main uncertainty source during gain measurement in such setup? |
| - | * During this laboratory we were investigating electronic noises. You have to remember that in real experiments You also have to fight with disturbances. Can You give an example of disturbances in real world ? | + | * During this laboratory we were investigating electronic noises. You have to remember that in real experiments You also have to fight with disturbances. Can You give an example of disturbances in real experiment? |
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