Electron Spin Resonance - Revision history

Wikiuser: /* Appendix */

2014-12-11T05:45:15Z

‎Appendix

Wikiuser: /* Schematic composition of the new setup */

2014-12-11T05:44:14Z

‎Schematic composition of the new setup

Wikiuser: /* Miscellaneous useful information about various parts */

2014-12-11T04:59:33Z

‎Miscellaneous useful information about various parts

Wikiuser: /* ESR measurements */

2014-12-10T19:56:52Z

‎ESR measurements

Wikiuser: /* Operating instructions */

2014-12-10T18:20:05Z

‎Operating instructions

Wikiuser: /* Miscellaneous useful information about various parts */

2014-12-10T18:09:27Z

‎Miscellaneous useful information about various parts

Wikiuser: /* Miscellaneous useful information about various parts */

2014-12-10T18:04:57Z

‎Miscellaneous useful information about various parts

Wikiuser: /* Miscellaneous useful information about various parts */

2014-12-10T18:04:30Z

‎Miscellaneous useful information about various parts

Wikiuser: /* Miscellaneous useful information about various parts */

2014-12-10T18:03:56Z

‎Miscellaneous useful information about various parts

Wikiuser: /* Main console */

2014-12-10T17:48:07Z

‎Main console

@@ Line 373: / Line 373: @@
 ==Appendix==
-In most of our troubleshooting series we did the analysis via data depiction and occasionally by fitting curves. The following links forward to the graphs that were used to investigate and interpret of various processes.
+In most of our troubleshooting series we did the analysis via data depiction and occasionally by fitting curves. The following links forward to the graphs that were used to investigate and interpret the various processes.
 '''Attenuator: conversion table'''

← Older revision		Revision as of 05:44, 11 December 2014
Line 370:		Line 370:

	Most of it should be performed pretty easily, however, the alignment such that all the numerous parts function together properly and do not irritate one another can be quite a challenge. At this point there is basically only one thing that prevents fast progress on the hardware section. The klystron or maybe even the entire magnet bridge does not respond to operating it without turning on the main console. Perhaps there is some essential communication among the two big experimental machines, which enables the klystron and the detector, respectively. Once that is resolved and there is an idea how to manipulate that or provide it externally, there should nothing be in the way to build the ESR setup like in the diagram.		Most of it should be performed pretty easily, however, the alignment such that all the numerous parts function together properly and do not irritate one another can be quite a challenge. At this point there is basically only one thing that prevents fast progress on the hardware section. The klystron or maybe even the entire magnet bridge does not respond to operating it without turning on the main console. Perhaps there is some essential communication among the two big experimental machines, which enables the klystron and the detector, respectively. Once that is resolved and there is an idea how to manipulate that or provide it externally, there should nothing be in the way to build the ESR setup like in the diagram.
−
−

	==Appendix==		==Appendix==

@@ Line 232: / Line 232: @@
 *main switch enables magnet bridge as well
 *main power cable at the bottom right corner on the back: top: ground, aside from the top: + and - electrodes (going through fuses and the get split into two, connecting to the main console and the magnet brigde without any "door", two lower prongs are connected (low resistance) on either sides (main console and magnet bridge), purpose is simply a mystery
-*turn down the magnetic field slowly (not more than 1000G in a jump) to prevent any damage to the electronics
+*turn down the magnetic field slowly (not more than 1000 G in a jump) to prevent any damage to the electronics
 |-
 |}

@@ Line 280: / Line 280: @@
 ==ESR measurements==
-We have a bunch of samples, which are supposed to be responsive to ESR. Unfortunately none of them, except two, are labeled or named. In the entire process of working on this project we tested numerous samples of this set. Most of them did not show any signal within the whole magnetic field scan range, however, at this point our skills on at which dial to chose which value was really limited. We tried to tune and optimize the quantities though, and dedicated quite a lot of time to consistency and the attempt to repeat ESR spectra with different materials. We investigated about 10 different samples, again with the new Lock-In setup as well, but we could not find any resonance with those materials.
+We have a bunch of samples, which are supposed to be responsive to ESR. Unfortunately none of them, except two, are labeled or named. Throughout the project we tested numerous samples of this set. Most of them did not show any signal over the entire magnetic field scan range, however, at that point our familiarity of the consoles was really limited. We tried to tune and optimize the quantities though, and dedicated quite a lot of time to consistency and the attempt to repeat ESR spectra with different materials. We investigated about 10 different samples, again with the new Lock-In setup as well, but we could not find any resonance with those materials.
 ===DPPH (Sample #1)===
-The strongest signal shows DPPH, the organic chemical compound 2,2-diphenyl-1-picrylhydrazyl. The absorbance of the incident microwave irradiation is really strong, such that the various parameters of the entire experiment loose their importance. As long as reasonable values for the numerous setting are chosen, one can find the strength of the magnetic field, where the dip in the by the cavity reflected power occurs - even when the magnetic field gets scanned kind of fast. Therefore, it's the perfect sample for the beginning and for ESR learners, because you receive a response for regulations far off the optimum. Moreover, always when something is changed at the experimental setup and it seems that it does not work appropriately any more, it is the sample to verify any issues, misalignment and damage.
+The strongest signal shows DPPH, the organic chemical compound 2,2-diphenyl-1-picrylhydrazyl. The absorbance of the incident microwave radiation is really strong, such that the various parameters of the entire experiment lose their importance. As long as reasonable values for the numerous setting are chosen, one can find the strength of the magnetic field, where the dip in the reflected power occurs - even when the magnetic field gets scanned kind of fast. Therefore, it's the perfect sample for beginning ESR, because you receive a response for regulations far off the optimum. Moreover, always when something is changed at the experimental setup and it seems that it does not work appropriately any more, it is the sample to verify any issues, misalignment and damage.
 One of our nicest DPPH spectrum is shown below. The figure depicts the linear sweep of the magnetic field strength as well, related to the sweep voltage:
@@ Line 307: / Line 307: @@
 ===ZnS (Sample #8)===
-In fact this sample not only contains inorganic ZnS (zinc sulfide), but it form a layer on a Silicon wafer. Since Silicon forms a perfect lattice, in theory, all that is observed ESR respond should originate from the ZnS coat. Though, everybody knows that practically there are no perfect crystals in nature. Hence, it is possible that signals arise as well from impurities in the Silicon lattice.
+This sample contains inorganic ZnS (zinc sulfide) coated on a silicon wafer. Since silicon forms a perfect lattice, in theory, any observed ESR response should originate from the ZnS coat. Though, it is understood there are no perfect crystals in nature. Hence, it is possible that signals arise as well from impurities in the silicon lattice.
-In fact, the exact magnetic field strength of this sample, we found by first looking up, where it should appear approximately. It is much weaker and therefore the influence of the experiment parameters are much more sensitive. If you are off the right setting by quite a lot, you will not obtain a clear spectrum. And due to the constant self-evolvement of the old setup, which was build, with all likelihood, decades ago, it is really tough to repeat one beautiful right away.
+In fact, the exact magnetic field strength of this sample, we found by first looking up where it should appear approximately. It is much weaker and therefore the influence of the experiment parameters are much more sensitive. If there is an incorrect setting, you will not obtain a clear spectrum. And due to the wear of the old setup, which was built with all likelihood decades ago, it is really tough to repeat a beautiful signal right away.
 After a long fight with the experiment setup and plenty of praying, we finally could measure a very nice spectrum of ZnS, how it is supposed to be:
@@ Line 315: / Line 315: @@
 [[File:ZnS_spectrum.JPG|center|700px|alt=A]]
-The ZnS spectrum was recorded not with the laptop oscilloscope, but with a normal external oscilloscope, which facilitate data export onto a flash drive. With the run on the laptop oscilloscope we noticed a high constant voltage intercept, which prevented us from zooming in deep enough by changing the volts per division. At one point the curve was simply off range. We utilized the original main console for this material, too. The scan values were
+The ZnS spectrum was recorded not with the laptop oscilloscope, but with a normal external oscilloscope, which facilitates data export onto a flash drive. With the run on the laptop oscilloscope we noticed a high constant voltage intercept, which prevented us from zooming in deep enough by changing the volts per division. At one point the curve was simply off range. We utilized the original main console for this material, too. The scan values were
 * Frequency (exterior wavecounter): n.a.
 * Attenuation: 16 dB
@@ Line 326: / Line 326: @@
 * Gain: 320
-By the way, technically ZnS should also have a so called side bands on both sides next to the main ESR peak. It can be the case that we can see them in the diagram above at about 3440 G and 3740 G. It is simply not possible to verify that they are symmetrically distributed aside from the main wiggle and that those are real resonance wiggles. The graph is not clear enough. Maybe due to unreliability of the apparatus we obtained that for approximately three consecutive scans. It is worth to spend some time on this later on, though.
+Technically ZnS should also have a so called side bands on both sides next to the main ESR peak. It can be the case that we can see them in the diagram above at about 3440 G and 3740 G. It is simply not possible to verify that they are symmetrically distributed aside from the main wiggle and that those are real resonance wiggles. The graph is not clear enough. Maybe due to unreliability of the apparatus we used for approximately three consecutive scans. It is worth to spend some time on this later, though.
 ===ZnS (Sample #9)===
-After numerous measurements of ZnS sample #8 we regognized that there is a little part of scotch take on it. And since we had another tube indicating that it contains the material ZnS, we tried to verify it with sample #9. At this point we already bypassed the old internal Lock-In by an exterior one. Therefore it was a test of that part at the same time.
+After numerous measurements of ZnS sample #8 we regognized that there is a little part of scotch take on it. And since we had another tube indicating that it contains the material ZnS, we tried to verify it with sample #9. At this point we already bypassed the old internal lock-in by an exterior one. Therefore it was a test of that device at the same time.
-Again, this sample it tough to deal with, because the resonance is quite weak and the manners of the old main console:
+Again, this sample it tough to deal with, because the resonance is quite weak along with the mannerisms of the old main console:
 [[File:ZnS_spectrum_2nd-sample.JPG|center|700px|alt=A]]
-As alreday mentioned above, this time we used the external Lock-In, but displayed the signal on the external oscilloscope, which we utilized for storing data as well.
+As mentioned above, this time we used the external lock-in, but displayed the signal on the external oscilloscope, which we utilized for storing data as well.
 The scan values were
 * Frequency (exterior wavecounter): 9.23216 GHz
@@ Line 353: / Line 353: @@
 Be aware of the somewhat different B-field axis: It is shifted by 25 G. Given that and a normal error both graphs are identical, regarding the main wiggle. Although, we did not reveal the two side dips, which seemed fairly consistent for the previous sample.
-The calculation of the magnetogyric ratio yields the value 1.843 &plusmn; 0.008 . Again, the error of the value for the magnetic field strength and mircowave frequency, when the resonance takes place, were both estimated as 0.2 %. In literature one can find various expectation values, based on the doping. None of the tested materials were pure ZnS. Therefore, it is impossible to evaluate whether the result is good or not.
+The calculation of the magnetogyric ratio yields the value 1.843 &plusmn; 0.008 . Again, the error of the value for the magnetic field strength and microwave frequency, when the resonance takes place, were both estimated as 0.2 %. In literature one can find various expectation values, based on the doping. None of the tested materials were pure ZnS. Therefore, it is impossible to evaluate whether the result is good or not.
 ==Desired and future ESR setup==

@@ Line 238: / Line 238: @@
 ==Operating instructions==
-Operating the ESR setup is relatively simple, as long as you obey the following steps. However, there are some essential things to do and a few things not to do, respectively. Review the tables of the recent section as well: [[#Miscellaneous other useful information about various parts|Link]]
+Operating the ESR setup is relatively simple, as long as you obey the following steps. However, there are some essential things to do and a few things not to do. Review the tables of the recent section as well: [[#Miscellaneous other useful information about various parts|Link]]
-Comply with this guidelines:
+Comply with these guidelines:
 ===Starting the machine===
-# Turn on the water cooling system to a decent flow rate. It is not necessary open the outlet lever entirely. In fact, that will cause quite a high pressure in the supply hose, perhaps leading to subtle damage. Moreover, longruns have shown that the outflow does not get warmer at all, even after hours at a quite high magnetic field strength.
+# Turn on the water cooling system to a decent flow rate. It is not necessary to open the valve entirely. That will cause quite a high pressure in the supply hose, perhaps leading to subtle damage. Moreover, long runs have shown that the outflow does not get warmer at all, even after hours at a high magnetic field.
 # Check else is shut down:
 ## Switch at the back of the magnet bridge, which hosts the klystron and the detector.
@@ Line 250: / Line 250: @@
 ## Magnetic field set value is zero.
 # Enable power switch on the lower left corner of the main console.
-# Clean your sample and place it inside the tube, made for holding the sample between the two magnet poles.
+# Clean your sample and place it inside the tube, made for holding the sample between the two magnets.
-# Change mode first to turn and then to operate. Wait for a while (up to one minute). Dial the frequency once in a while and see whether the two scales AFC output and detector current respond. When they react to changes, set the AFC to zero. The frequency of the klystron equates the resonance frequency of the cavity now.
+# Change mode first to tune and then to operate. Wait for a while (up to one minute). Dial the frequency once in a while and see whether the two scales AFC output and detector current respond. When they react to changes, set the AFC to zero. The frequency of the klystron equates the resonance frequency of the cavity now.
 # Adjust the Iris height by screwing the stick in or rather out. The aim is to minimize the detector current which correspond to the total power of reflected microwaves (The past has shown that the height ranges at approximately 3-4 rotations from closed entirely).
 # Align the height of the sample inside the tube. The sample is sitting in the center of cavity and hence has an effect on the resonance frequency of the cavity. For the measurement later on, it is very desirable to reduce it to a minimum. The sample pipe is put into the holder tube by a little ring, which prevents it from falling into the tube. Carefully change the position of the ring and always put the sample pipe back and see where the AFC stops. You want the AFC to be as left as possible. This step is really sensitive. Normally the AFC changes just by pulling the sample pipe out and inserting it back, without sliding the ring. Even rotating the sample interacts with the AFC, especially when the material is not distributed uniformly at the very bottom of the pipe. That is the case for materials other than liquids and powders, for instance little solid plates.
 # Check the Iris again (optional)
-# Chose a value for Gain: Too low leads to inability to distinguish whether whether there is a signal or not; Too high values correlate tot a lot of crazy noise; Good starting value: 100 - 1000
+# Choose a value for Gain: too low leads to inability to distinguish whether there is a signal or not; values too high correlate to excess noise; Good starting value: 100 - 1000
-#Chose your Modulation Amplitude: Too small choice will not excite any transitions; Too great values are related to unnecessary broadening of the absorption wiggle, for better resolution this area should be as narrow as possible; Good starting value: 1 - 4 G (10 - 40 G for weak samples)
+#Choose your Modulation Amplitude: A value too small will not excite any transitions; values too great are related to unnecessary broadening of the absorption peak, for better resolution this area should be as narrow as possible; Good starting value: 1 - 4 G (10 - 40 G for weak samples)
-# Set the Signal Filter: Too little choices will let a lot of useless signal pass; Too high values will lead to a cut-off of the desired signal; Good starting value: position 4 - 10
+# Set the Signal Filter: a small time constant will let a lot of useless signal pass; a large time constant will lead to a cut-off of the desired signal; good starting value: position 4 - 10
 # Select your Scan Time: Longer enhances resolution later on and too short disable the opportunity to detect the transition (however, it depend also on the magnetic field scan range); But longer is not always good, especially when your setup shows a drift in any of the other components: Good starting value: 1 minute
 # Set the magnetic field start value and the sweep interval.
@@ Line 272: / Line 272: @@
 # Power off the magnetic field.
-# Switch the mode from operate to tune (on the magnet bridge). Afterwards spin the know even more to standby mode.
+# On the magnet bridge, switch the mode from operate to tune then to standby
 # Take your sample out of the cavity and store or shelf it.
 # Disable magnet bridge by switch at the back.
 # Press main power switch on the main control panel.
 # Close water supply.
 ==ESR measurements==

@@ Line 166: / Line 166: @@
 |-
 |Frequency dial
 |hard to read, suggested to crouch down and read the meter head on
 |-
 |Detector current
 |does not go to zero, but minimum is at about 40
 |-
 |AFC voltage
 |works only in vicinity of the resonance, otherwise crazy
 |-
 |Modulation coils
@@ Line 206: / Line 209: @@
 |-
 |Gain
 |not sure whether it works alright, maybe facilitating drift as well
 |-
 |Modulation amplitude
 |seems that great set values enhance signal drift
 |-
 |Signal filter
 |there are more knob position (20) than numbers written around it (16), although, the numbers might be the time of a low pass filter
 |-
 |Pen level
 |seems to drift slowly, depending on the Gain value up or down
 |-
 |Side scan panel
 |sweep is driven mechanically through the old XY-recorder on the horizontal panel, there is a mechanism below that board
 |-
 |Miscellaneous

@@ Line 162: / Line 162: @@
 |Attenuator
+|
-*verified to function properly revealed by nice exponential dependence, like one expects for a decibel based scale (review appendix or klick on the [[Media:Detector_dial_current-voltage-attenuator.pdf|Link]])
+*verified to function properly revealed by nice exponential dependence, like one expects for a decibel based scale (review appendix or click on the [[Media:Detector_dial_current-voltage-attenuator.pdf|Link]])
-*for easier incident power estimation there is a converion table in the appendix or klick on the [[Media:Attenuation_conversion.pdf|Link]]
+*for easier incident power estimation there is a conversion table in the appendix or click on the [[Media:Attenuation_conversion.pdf|Link]]
 |-
 |Frequency dial
-|hard to read, suggested to crouch down and read the meter head on
+|*hard to read, suggested to crouch down and read the meter head on
 |-
 |Detector current
-|does not go to zero, but minimum is at about 40
+|*does not go to zero, but minimum is at about 40
 |-
 |AFC voltage
@@ Line 176: / Line 176: @@
 |Modulation coils
+|
-*the power needed to apply the 40 G maximum is approximately 2 A at 5 V (review appendix or klick on the [[Media:Modulation_coils_voltage-current-supply-resistance.pdf|Link]])
+*the power needed to apply the 40 G maximum is approximately 2 A at 5 V (review appendix or click on the [[Media:Modulation_coils_voltage-current-supply-resistance.pdf|Link]])
 *can get really hot, since the two tiny magnets are not water cooled
 |-
@@ Line 186: / Line 186: @@
 |Miscellaneous
+|
-*does not function without the main console switched on, even though it gets power from the wall outlet, since the main power cable going into the main control panel is split into two circuits, one connectiong into the main console and the other one directly into the magnet bridge without any "door"
+*does not function without the main console switched on, even though it gets power from the wall outlet, since the main power cable going into the main control panel is split into two circuits, one connecting into the main console and the other one directly into the magnet bridge without any "door"
-*water drain manages the water flow rate for at least a couple of hours, although, with the water never turned on entirely; it is simply not necessary and thereby preventing damage
+*water drain manages the water flow rate for at least a couple of hours, though the water was never turned on entirely; it is simply not necessary and helps prevent damage
 *in general, the whole magnet bridge apparatus looks good with respect to reliability and functionality
 *when swapping samples, it is suggested to change the magnet bridge to 'tune', as it may damage the detector crystal
@@ Line 200: / Line 200: @@
+|
 *must be turned slowly
-*applies DC current through side prongs, aside from the top one, of cable on the buttom right corner of the back
+*applies DC current through side prongs, aside from the top one, of cable on the bottom right corner of the back
 *coils are in series: output of one spool is the input of the other one
 *resistance: about 1.1 ohm each coil
-*power supplied: about 18 V at 6000: about 18 Ampere total going through both coils (review appendix or klick on the [[Media:Magnets_voltage-current-supply.pdf|Link]])
+*power supplied: about 18 V at 6000 G: about 18 Ampere total going through both coils (review appendix or click on the [[Media:Magnets_voltage-current-supply.pdf|Link]])
 |-
 |Gain
@@ Line 218: / Line 218: @@
 |-
 |Side scan panel
-|sweep actually is driven mechanically through the old data plotting pen type thing on the horizontal panel, there is a mechanism below that board
+|sweep is driven mechanically through the old XY-recorder on the horizontal panel, there is a mechanism below that board
 |-
 |Miscellaneous
+|
 *main switch enables magnet bridge as well
-*main power cable at the buttom right corner on the back: top: ground, aside from the top: + and - electrodse (going through fuses and the get split into two, connecting to the main console and the magnet brigde without any "door", two lower prongs are connected (low resistance) on either sides (main console and magnet bridge), simply a mystery
+*main power cable at the bottom right corner on the back: top: ground, aside from the top: + and - electrodes (going through fuses and the get split into two, connecting to the main console and the magnet brigde without any "door", two lower prongs are connected (low resistance) on either sides (main console and magnet bridge), purpose is simply a mystery
-*turn down the magnetic field slowly (not more than 1000G in a jump) to prevent any damage to the electronics.
+*turn down the magnetic field slowly (not more than 1000G in a jump) to prevent any damage to the electronics
 |-
 |}
 ==Operating instructions==

@@ Line 123: / Line 123: @@
 ====Main console====
-For concrete illustration of the main control panel review this table.
+For concrete illustration of the main control panel review this table. Anything in <span style="color:blue">blue</span> has been eliminated by using other devices, specifically a lock-in amplifier.
 {| class="wikitable"
@@ Line 129: / Line 129: @@
 |-
 |Main B-field - DC B-field
-|sets the initial magnetic field, before the sweep, that is, the starting strength of the B-field sweep
+|sets the initial magnetic field, before the sweep. That is, the starting strength of the B-field sweep
 |-
-|Gain
+|<span style="color:blue">Gain</span>
 |amplifies the detection signal to expose by noise hidden real signal
 |-
@@ Line 137: / Line 137: @@
 |regulates the amplitude of the 100 kHz current sent to the modulation coils
 |-
-|Signal filter
+|<span style="color:blue">Signal filter</span>
 |functions as a low pass filter for resolution purposes
 |-
-|Pen level
+|<span style="color:blue">Pen level</span>
 |provides a voltage offset going to the recorder/data acquisition
 |-
 |Side scan panel
-|tunes the time parameters reglating to the sweep settings
+|tunes the time parameters regulating the sweep settings
 |-
 |}
 ====Miscellaneous useful information about various parts====