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Operation Instructions for the ESP380E

A short introduction to operate a pulsed EPR spectrometer

(January 2002)

by

MATTHIAS WEBER

Matthias Weber Operation Instructions for the ESP380E

Table of Contents

1 Introduction................................................................................................................4

2 General Procedure to Operate the ESP380E..........................................................4

2.1 Tuning Procedure.................................................................................................52.2 Getting started: Setting up the Experiment (Recording of a FID).......................62.3 Shut down Procedure...........................................................................................92.4 Complete Shut down Procedure..........................................................................92.5 Turning on Procedure........................................................................................102.6 Acquire Data by Using the PulseSPEL.............................................................11

2.6.1 Using a PulseSPEL Program and Setting it up.....................................................112.6.2 Differences between Acquire Data with the Oscilloscope and the SDI Board....14

3 Calibration Procedures...........................................................................................15

3.1 Phasing the Pulse Channels...............................................................................153.2 Checking the Phasing of the Channels..............................................................171.1 Setting up a /2 (90) Pulse................................................................................181.4 Determining "D0"..............................................................................................19

4 Appendix...................................................................................................................21

4.1 Important Information.......................................................................................244.1.1 Pulse Spectrometer Parameters ("P" – "Q" – "D")...............................................244.1.2 Important PulseSPEL Programs...........................................................................244.1.3 Editor Key bindings..............................................................................................264.1.4 OS/9 Commands...................................................................................................26

4.2 Sample Spectra..................................................................................................284.2.1 DPPH (one pulse sequence).................................................................................284.2.2 Coal (two pulse sequence, electron spin echo).....................................................304.2.3 Irgacure 651..........................................................................................................314.2.4 FID Signal with no Sample (ringing)...................................................................33

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4.3 List of Components............................................................................................344.4 List of Literature................................................................................................37

4.4.1 EPR.......................................................................................................................384.4.2 Pulsed ENDOR.....................................................................................................404.4.3 NMR.....................................................................................................................414.4.4 My favorite books.................................................................................................42

4.5 Persons at Bruker...............................................................................................424.6 FlexLine Manual................................................................................................44

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1 Introduction

This script should serve as a general guide for operating the FT-EPR spectrometer. It is necessary that everybody using the spectrometer has read the manual and familiarized with the OS/9 operating system, LeCroy oscilloscope and the main parts of the spectrometer. Several manuals are around in our Lab (around 14 manuals, xxx binded books and a box filled with useful materials (letters, emails, etc.) on the shelf to the left of the FT EPR spectrometer), which help you to understand the spectrometer. Further, you can take a look in some of my group meeting presentations, which are reflecting some of my experiences with pulsed EPR and contain additional information. In this "manual" you will find no information about how to use the spectrometer in the CW mode because it will dramatically change after the upgrade to the ESP580. If somebody plan to do such kind of experiments before the upgrade she/he should contact Zhiqiang Liu. I hope everybody understand this script as a ‘living’ document which should be extended by your own experience (comments and corrections are also welcome).

2 General Procedure to Operate the ESP380E

There is a very good description in the manual "User's Manual ESP380E" (Safety Guide, pages 1 - 9) how to tune and get started the spectrometer which should be read before. In the following you will find a summary of these instructions together with some background information and tips. In addition, a help can be activated by pressing "F4" for the microwave bridge controller or "F10" for the spectrometer menus (e.g. key bindings, button locations, etc.). Consult these helps before using a "try and error" procedure.

2.1 Tuning ProcedureThe tuning procedure is briefly described below and has to be repeated each time after changing of a sample.

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Install the FT cavity (FlexLine ring resonator) and the He-cryostat (the cryostat is in principle not necessary but it is an additional shielding against leaking microwave radiation). An aluminum tube has to be used in order to mount the cavity without the cryostat (see the appendix for details)

Insert the sample in the cavity (see FlexLine manual for instructions) Tuning the cavity

switch "CW" and "STAB" on (ESP380 controller unit) make sure that the red LEDs of the video amplifier gain and the bandwidth are on go from "Stand By" in the "Tune Mode", set "BIAS" (potentiometer) to zero

(counterclockwise, diode current goes to zero/left), decrease the attenuation to 15 dB. You should see one sharp peak in absorption (stabilizer) and one broad peak in emission (you can change between the microwave bridge controller and the spectrometer controller by pressing "F3" (changing between upper and lower screen). The active windows is marked by a white frame)

increase Q-value of the cavity by pushing up the satellite arm of the resonator. You should see that the broad line becomes more and more sharp by going to higher Q-values. If you do not see the a sharp line coming up then change the microwave frequency (with the "FREQUENCY" potentiometer on the pad) as long you see the peak! (Typical values of the microwave frequency are around 9.60 – 9.66 GHz).

Decrease the Q-value as much as possible by pushing up the satellite arm of the cavity

Bring the sharp peak to the same position as the broad peak determined before (ignore other broad peaks which could be observable) by changing of the stabilizer frequency at the console ("STAB. FREQ")

bring both peak in the middle to the screen ("FREQUENCY" knob on the pad) and switch to operate

adjust the "Lock Offset"-value of the microwave bridge to zero (middle position) by turning the "FREQUENCY" potentiometer, set attenuation back to 60 dB and increase the "BIAS" (diode current goes to the right)

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2.2 Getting started: Setting up the Experiment (Recording of a FID)

Please follow up this procedure every time before performing any pulsed sequences in order to be sure that the microwave bridge and the amplifiers are working fine.

on the ESP 380 controller turns the following buttons in the following direction: a) CW off; b) QUAD on; c) HPP on and d) AMP on

turn on the TWT bridge (microwave amplifier) and it takes several minutes to reach the "Stand By" mode (green light on, voltage = -0.08 V)

turn on the oscilloscope and set the trigger on external and both channels (traces "e" and "f") are active and set to the "continuos" mode (can be done by pressing "redefine" on the oscilloscope)

set video amplifier gain to 48 - 60 dB and bandwidth to 200 MHz, microwave power attenuation should be higher than 80 dB, connect cables DS1 and DS2 to the two channels of the oscilloscope (channels are set to an impedance of 50 or 1M plus an additional terminator of 50 )

be sure that you are in the main menu (press several times the "ESC" key) and then go to "Pulse Pattern Definition" menu by pressing "P" twice

press either "+" or "–" to switch to the "+x"–channel program a single pulse (pulse position = 0 ns, pulse length = 16 ns) by editing the

table (press "E" to edit and "ESC" to leave this mode) further you have to program the "SDI"–channel (for triggering of the oscilloscope)

with a pulse position of 0 ns and a pulse length of 80 ns all other channels should contain only zeros (check all channels) calculate all necessary pulse positions and delays (defense pulse, TWT pulse, etc) by

pressing "I" (invoke pulse pattern) and start the pulse programmer with "A" at least one of the two channels should show the defense pulse on the oscilloscope

(probably you have to turn the "PHASE" potentiometer of the microwave bridge to see the defense pulse clearly). An example trace is shown in the manual "User's Manual ESP380E", section "Safety Guide" on page 6

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IF YOU DO NOT SEE THOSE DEFENSE PULSES DO NOT PROCEED ANY FURTHER AS IT WILL DESTROY THE DETECTORS

instead, repeat the procedure above (probably you did a mistake or a part of the spectrometer is not working properly) and if this doesn't help you have to call Bruker for help (see list of persons to contact in the appendix)

if you do see the defense pulse turn the TWT bridge into the operate mode by pressing "OPERATE" button on TWT (make sure the attenuation of the microwave pulse is higher than 80 dB, CW is off and the magnetic field is set far away from any resonance lines of the samples). The cathode voltage should be around V = –11.46 V in full operation

you should see the microwave pulse in the defense pulse. Decrease slowly the microwave pulse power to 3 - 10 dB and keep an eye on the oscilloscope. Stop increasing the microwave power if a signal is appearing direct after the defense pulse and you are sure that there should be no EPR signal near the chosen field position (e.g. set field to 50 G) and do the following: Increase the attenuation of the high power attenuator back to 80 dB, stop the pulse programmer and set the TWT bridge to "Stand By". A to high Q-value of the cavity can cause "these signals" (called "ringing" and comes from the strong microwave pulse). You have to shut down the bridge (see paragraph 5.5) and start the tuning procedure again. If this doesn't help you have to call Bruker (probably the cavity is damaged)

if the ringing does not exceed the noise level you can proceed. Decrease the attenuation of the video amplifier to 30 dB and increase the magnetic field stepwise by setting it to 1000 G - 2000 G - 3000 G - resonance field (usually around [email protected] GHz for carbon centered radicals) with breaks of several seconds

if the magnetic field is close to a resonance line (10 G) the FID signal can be observed. For DPPH the FID should look like an exponential decay (on-resonance condition, one single line). By adjusting the signal phase ("SIG. PHASE") you should be able to put all the signal into just one channel of the oscilloscope (usually in channel 1, which is the real part)

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the pulse programmer can be stopped by pressing (“P" – “P” –) “Q”

!The spectrometer is now set up for operating in the pulsed mode!

2.3 Shut down ProcedureThe procedure to shut down the spectrometer is in principle to follow the procedure described above in an opposite direction that means in short:

set attenuation of the high microwave power attenuator to higher than 80 dB make sure that the pulse programmer is stopped (press “P” – “P” – “Q” from the main

menu) set attenuation of the video amplifier to 0 dB and the bandwidth to 25 MHz press “Stand By” button of the TWT bridge (wait until the voltage is around –0.1 V) on the ESP 380 controller turns the following buttons in the following direction: a)

AMP off; b) HPP off; QUAD off and CW on (make sure the attenuation of the microwave pulse is higher than 80 dB and the TWT bridge is in “Stand By” (green light)).

decrease magnetic field stepwise (3000 G – 2000 G – 1000 G) to 50 G Activate the microwave bridge controller window (press “F3”) and bring the

microwave bridge to “Stand By” switch off the TWT bridge and the oscilloscope, set the “STAB” to off and reduce the

screen light of the monitor

2.4 Complete Shut down Procedure Make sure an experiment is not in progress Make sure the microwave controller is on "Stand By" Make sure all the spectra are saved. You can check who has been using the

instrument by looking at the EPR logbook or the calendar near the EPR

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IMPORTANT: Press the LOC button on the ER032 M Field Controller unit. Type in 50 (using the numeric keypad on the Field Controller) and press CF (this sets the magnetic to its minimum)

IMPORTANT: Press the LOC button on the ER023 Signal Channel unit. Then press MA key. Now press the double arrows pointing downward () several times until you see the MA OFF message displayed.

Turn off the DC key on the ESP 380 FT-EPR unit if it is on. The key is on the lower left corner and turning it counter-clockwise turns the DC power off.

Turn off the monitor. Turn off the DC power to the ESP 300 data system by turning counter-clockwise the

key located at the lower right side at the back of the ESP 300 (CW unit) console Turn off the DC power switch at the back (a little left and up from the DC key) of the

ESP 300 (CW unit) console to off position. Important: Press on the red OFF button on the ER082C magnet power supply (by the

window)Turn all the circuit breakers off by turning them down. The circuit breakers are located at the back if the ESP 300 (CW unit) console at the very bottom.

2.5 Turning on ProcedureFollow the steps described in paragraph 2.4 (except for #5 and #4 and skip #6)

2.6 Acquire Data by Using the PulseSPELPulseSPEL is the most convenient way to use the spectrometer because this language allows automating the setting of the delay times, pulse positions and the acquisition procedure and extend the possibilities of the spectrometer. The PulseSPEL programs can be used also after the upgrade (probably with some modification). Therefore, it is important to understand this language. Both acquisition methods (oscilloscope and the SDI (sampling digitiser) of the spectrometer) can be controlled with PulseSPEL. The chapter in the manual should be read before using this language in order to set the variables with the right values.

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2.6.1 Using a PulseSPEL Program and Setting it up go to the main page (pressing several times "ESC") and go to the "pulse experiment

definition" by pressing "P" – "W" press "I" to set the directory (location of the programs), type the directory name (eg.

"/h0/pulsespel/spel2"), press enter and choose the desired program (eg. "fidCYCLOPS"). A list of important programs can be find in paragraph 5.1.2

if a previous program was loaded you should go to the "File handling" menu (pressing twice "ESC" and then "F") and delete the page (pressing "D") and go back to "pulse experiment definition" ("ESC" – "P" – "W")

take a look to see the names of the variables and/or edit the program by pressing "E" (a short description of important key bindings for the editor can be find in paragraph 5.1.3

after leaving the editor (pressing "ESC" and type "EX" + pressing "ENTER" to save the changes in memory) the program will be tested and shouldn't show any errors (if you would like to save the program on disc then press "O". Do this only if you want the changes permanently for future experiments.)

press "V" (check with validation) to set up the experiment and validate the program (it is like a test run without performing the experiment). The validation has to be successfully otherwise the experiment can not be started. Common errors are the following: the descriptor file (this file defines the variables and the corresponding values) is

not loaded. Press "P" to read out the file "descr.def" (if the file cannot be found then change to a directory which contain the file like "/h0/pulsespel/mwspel")

variables containing values which are not matching with the experiment (overlapping of pulses, not fulfilling the 8ns time raster). Press "G" to edit the values and variables. Leaving the editing mode by pressing "ESC" and type "EX" and complete the command with "ENTER". An understanding of the PulseSPEL language is unavoidable at this point

go to the main menu (pressing "ESC" twice) and enter the acquisition menu in order to perform a pulse experiment (press "A" and then "Q"). Make sure that the

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oscilloscope is on, both channels are activated (traces "e" and "f"), in the "summed" mode (for the case of using a pulse program together with the LeCroy) and set to the same scale ("V/div" – value). If you had pressed "Q" and then see the message "PulseSPEL experiment aborted: Trace FE/FF off" on the bottom of the screen then you forgot to switch on one or both of the traces of the oscilloscope.

press "H" if you want to change some parameters (e.g. d0). In order to see the value of a variable just type the name (e.g. "D0") and complete the command with "ENTER". The value will then displayed. For changing the value of a variable you have to type the name followed by the desired number (with a blank between them) + "ENTER" (e.g. "D0 200" means that "d0" will be set to 200). All times are in ns and keep in mind that the current system has a 8ns time raster (e.g. for the microwave pulse length p0, p1, etc)). This menu can be left with pressing "ESC"

it is possible to change some settings in this pulse experiment menu like autoscale "S", verbose "V", continuos mode "C", etc.

press "G" to start the experiment. the pulse programmer stops automatically after the experiment and switches to the

acquisition menu

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2.6.2 Differences between Acquire Data with the Oscilloscope and the SDI Board

different commands in the PulseSPEL language to acquire data (only important if you want to make your own program otherwise you load a program with the corresponding extension ("SDI" for the internal digitiser board)). Compare the example below for the differences. Both are for acquire a FID signal with phase cycling. The right one is using the oscilloscope and the other one the SDI board

; FID detection with SDI;begin defs dim s[1024,1]end defs;begin lists ph1 +x -x +y -y asg1 +a -a +b -b bsg1 +b -b -a +a;end list;begin exp [quad sdi] sweep x=1 to sx p0 [ph1] d0 dx acq [sg1] dx=dx+8 next xend exp

; FID detection with LeCroy ;begin defs dim s[1024,1]end defs;begin lists ph1 +x -x +y -y asg1 +a -a +b -b bsg1 +b -b -a +aend lists;begin exp [quad lecroy]; p0 [ph1] d0; dig [sg1];;end exp

the SDI has to be switched on at the console ("DIG" on) for using the SDI board make sure that the cable "S1" and "S2" are connected to the SDI board (module ESP

1600 - 1078, back of the console)

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3 Calibration Procedures

3.1 Phasing the Pulse ChannelsThe best results are available if all four microwave channels (+x, –x, +y and –y) are well phased because this is important for the phase cycling algorithm in order to eliminate unwanted signals. The phases of the channels should be +x = 0, –x = 180, +y = 90 and –y = 270. The procedure to phase the channel is the following: bring the microwave bridge in a safe mode (TWT amplifier in "Stand By", high

attenuation for the microwave power, video amplifier attenuation to zero. the bridge should be tuned and the console in the FT mode connect the transmitter monitor cable (labeled with "TM") to channel 1 of the

oscilloscope and set the channel in a continuos mode. The transmitter monitor allow to detect the output of the TWT amplifier and therefore can visualize the form of the pulses

go from the main page to the pulse pattern definition menu (press "P" - "P") and program the following pulses:

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channel pulse position / ns pulse length / ns+x 0 24-x 200 24+y 400 24-y 600 24

This pattern allows to detect the TWT amplifier output of all four different channels

press "I" and then "A" to start the pulse programmer four pulses with a length of 24 ns and a distance of 200 ns should be visible on the

screen (probably it is necessary to change some settings of the oscilloscope and/or the phase of the transmitter monitor " monitorI" to see the signals)

set the leveler of all four channels to 10.0 (screw knobs on the ESP 380 controller unit)

set the phase of the '+x'–channel to 0.0 (phases are relative to a reference and therefore we define this channel as our reference)

turn the " monitorI" knob (phase of the transmitter monitor) in a position that there is no transmitter signal from the '+x'–channel visible on the oscilloscope

change phase of the '–x'–channel as long that there is also no transmitter signal visible from the '–x'–channel

check the phase of the '–x'–channel (if it is 0 or 180 relative to the '+x'–channel) by turning the " monitorI". The '+x'–channel should show a positive signal and '–x'–channel a negative one (or vice versa)

maximize the signal of the '+x'–channel by changing the transmitter phase (turning the " monitorI" knob)

change phase of the '+y'– and '–y'–channel as long that there are no transmitter signals are visible from these two channels (turning the corresponding phase knob which are signed by )

check the phase of the '+y' and '–y'–channel (if it is 90 or 270 relative to the '+x'–channel) by turning the " monitorI". The '+y'–channel should show a positive signal and '–y'–channel a negative one (or vice versa)

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3.2 Checking the Phasing of the Channels insert the DPPH sample in the cavity, tuning the microwave bridge and setting up the

spectrometer make sure that the cable "DS1" and "DS2 are connected to the oscilloscope set the high microwave power attenuator to 4 dB, the receiver gain to 30 dB, and the

bandwidth to 200 MHz set magnetic field to the resonance line and put all the signal in the real channel and

nearly no signal in the imaginary channel by adjusting the "SIG. PHASE". The signal in real channel should looks like an exponential decay (like in the manual on page 9 in the "Safety Guide" section)

set the pulse timing as shown in the following table:

channel pulse position / ns pulse length / ns+x 0 16-x 1000 16+y 2000 16-y 3000 16

change the setting of the oscilloscope in order to display all four pulses. You should see the following after the different pulses:

+x –x +y -yreal part positive FID negative FID no FID no FIDimaginary part no FID no FID positive FID negative FID

Probably it is necessary to do a fine adjustment of each the '+y'– and '–y'–channels by changing a little bit the phase of the corresponding channels

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3.3 Setting up a /2 (90) PulseHow much a microwave pulse rotates a spin system depends on the pulse length and the used microwave power. Because both depending on each other one keeps one fix and change the other parameter. I usually keep the pulse length fix (16 ns for a maximal bandwidth) and adjust the microwave power. insert a your sample tune the microwave bridge and set up the spectrometer (paragraph 2.1-2.2) when possible choose conditions that you observe only one single EPR line for

simplifying the procedure set magnetic field to the resonance line and set the "SIG. PHASE" that all the signal

appears in the real channel (as an exponential decay) and nearly no signal in the imaginary channel

change the attenuation for the high microwave power on the console until you get a signal maximum in the real part

a good 90º pulse is given at a microwave power giving the strongest signal, therefore, the above determined microwave power correspond to a 90º pulse

a 180º pulse gives no signal for a single line in the real channel (as long everything is tuned very well) and therefore in most cases it is easier to determine the microwave power for a 180º (vanishing signal) than a 90º pulse (maximum of signal intensity). This can be done by programming a two times longer pulse or by increasing the microwave pulse to a 180º pulse and than reduce the power by a factor of 2 (3 dB of attenuation)

typical values are around 3 - 6 dB (depending on the sample)

3.4 Determining "D0"

"D0" is a variable, which determine the delay time between triggering the instrument and triggering the data acquisition in the PulseSPEL experiments. Therefore, it can be used to adjust the zero time of the signal traces (for example "zero time" for the FID will be in the middle of the microwave pulse). This parameter has to be adjusted for each pulse

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sequences and bandwidths but it is independent on the sample. Once determined it can be used for all samples and has only to be remeasured after changing time/pulse definitions (menu "P" - "Q" - "D", pulse spectrometer parameters). insert the DPPH sample for single pulse detection (FID) or the coal sample for

mutiple pulse detection (electron spin echo) in the cavity tune the microwave bridge and set up the spectrometer (paragraph 2.1-2.2) set magnetic field to the resonance line and set the "SIG. PHASE" that all the signal

appears in the real channel (as an exponential decay for a FID) and nearly no signal in the imaginary channel

change the magnetic field to 20 G off-resonance record the FID or the ESE signal by using the corresponding PulseSPEL program

(paragraph 2.6) with d0 = 0ns. (press "A" - "Q" from the main menu and the "G" for the acquisition) The recorded traces should show the decays overlayed with an cosines like oscillation and one or more microwave pulses

load the external "dead_time" module by going to the module menu "A" - "M" and press "D". (It is necessary that the external module was assigned before on "D" which can be done by pressing "*", command index = "D" and name = "dead_time")

press "S" (to shift the trace) and the screen will split in two parts. The upper part shows the real part of the spectrum as recorded and the other one the corresponding spectrum after Fourier transformation

Shift the spectrum (press "N" and input a number) as long the resonance line is in the right phase (in absorption)

The number of points, which were necessary to bring the spectrum in the right phase is corresponding to d0 and can be converted to a delay time by multiplying the number of points by 2.5 ns. That means, "D0" is given by:

D0 = 'number of points' * 2.5 ns exit this module and go to the main menu by pressing "ESC" several times press "A" - "Q" to perform a pulse experiment and change the value for D0 (press

"H", then type "D0 value_determined_above" and complete the command with "ENTER")

press "ESC" to exit this menu and perform the pulse experiment (press "G")

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go to the data manipulation menu ("D" - "V", this menu will not be discussed in this script) and press "1" to do the 'Forward Fourier Transformation'.

The spectrum after transformation should show the spectra with the right phase. Acquire several spectra at different field positions. At each field position you should

get a spectrum with the right phase. Typical value for d0 are around 300 ns (single pulse, 200 MHz, pulse length p0 = 16ns: d0 = 286 ns; 2 pulse sequence, 200 MHz, pulse lengths p0 = 16 ns, p1 = 24ns: d0 = 306 ns)

4 Troubleshooting

The following chapter is a collection of typical errors (from my experience) and how to solve them:

Symptom: Microwave cannot be set to operate or goes in the stand by mode after a while

Solution: The heat exchanger is not running in most of such cases. Check the power supply and the water level. Is the tap water on and cold?

Symptom: Cavity cannot be tuned (no dip)Solution: The lost of microwave can be very high by using huge sample and

solvents with high polarity (like water). In these cases the cavity cannot be tuned properly. Check at first if you can tune the cavity without the sample. Reduce the diameter of your sample and use a less polar solvent if possible. In principle, you can use the spectrometer if you cannot tune the cavity very well but signals will be much lower

Symptom: No defense pulse after tuning

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Solution: Check the microwave bridge: Is the CW-microwave power set to 60dB? Is the bridge in the "OPERATE" mode? Is the “BIAS” set to maximum? Repeat the tuning procedure (see section 2.1).

Symptom: Ringing after the defense pulseSolution: Cavity has a too high Q-value. Try to push up the satellite arm more (at

the cavity) to reduce the ringing. If this doesn’t help then you have to increase the pulse length of the defense pulse. Go to the “Pulse Spectrometer Parameters” menu (press "P" – "Q" – "D") and change the corresponding entry (see 5.1.1 for typical values). I never changed these parameters for my experiments, which means that something is wrong with the cavity if you have to do it. Call Bruker, probably the cavity is damaged.

Symptom: No signals from sampleSolution: several things can cause this error. Test the spectrometer with the DPPH

or coal sample. Typical errors are the following: Sample is not in the right position Switch TWT amplifier if off Microwave pulse power is too low Wrong triggering of the oscilloscope

Symptom: No or weak signals by photochemical radical generationSolution: Check all your delay times, probably you try to apply a microwave pulse

before the laser pulse. Check also the cable to the laser and all connections. Is the red light diode active on the 'ESP 385 - 1010'-board? Is the instrument set to external triggering ("P" - "A")? Do you trigger the laser by the instrument or the laser the spectrometer (is everything setup for that?)? Are you using the right out- and input ports? Is the syringe pump working?

Symptom: No or weak signals by photochemical radical generation

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Solution: Check all your delay times, probably you try to apply a microwave pulse before the laser pulse. Check also the cable to the laser and all connections. Is the red light diode active on the 'ESP 385 - 1010'-board? Is the instrument set to external triggering ("P" - "A")? Do you trigger the laser by the instrument or the laser the spectrometer (is everything setup for that?)? Are you using the right out- and input ports? Readjust the laser light? Check the type of your cell/tube (quartz or glass)

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5 Appendix

5.1 Important Information

5.1.1 Pulse Spectrometer Parameters ("P" – "Q" – "D")The following table contains typical values for a save operation of the spectrometer

Ch function delay length Ch function delay length1 Pulse Gate 240 8 9 +x 200 02 CW Arm 0 0 10 +<x> 200 03 Decoupler 160 112 11 –x 200 04 Def. Pulse 112 232 12 –<x> 200 05 TWT 0 152 13 +y 200 06 SDI 0 0 14 +<y> 200 07 Channel 7 0 0 15 –y 200 08 Channel 8 0 0 16 –<y> 200 0

5.1.2 Important PulseSPEL ProgramsPulseSPEL programs can be found in /h0/pulsespel/speln (n = 1, 2, 4): These are the original PulseSPEL programs from

Bruker /h0/pulsepel/mwspel: These are my personal written or often used programs /h0/spel_alt/name: These are the old PulseSPEL programs from Bruker before the

hard drive crashed and there are additional programs from Igor Koptyug and Ralph Weber

Often used programs (extension "ext" means external instead of the internal one; SDI means the use of the internal SDI board instead of the oscilloscope):


fidCYCLOPS: Recording of a FID signal using a 4-phase cycling routine to eliminate unwanted signals

fidSWEEPext: Recording of several FID at different field position with a step width of nG (variable "bcsteep(n)") and using an external trigger

echo_fullcycle: Recording of an electron spin echo (ESE) by using a two pulse sequence and a 8-phase cycling routine.

echoSWEEPext: Recording of several ESE at different field position with a step width of nG (variable "bcsteep(n)") and using an external trigger

echo_8_SDI: Recording of an electron spin echo (ESE) by using a two pulse sequence and a 8-phase cycling routine and the SDI board instead of the oscilloscope.

ESEEM_SDI: Program to measure the relaxation time TM (detection of the ESE signal in dependence of the delay time between the two microwave pulses) with 8-phase cycling routine

2p_T1_SDI: Program to measure the relaxation time T1 (detection of the ESE signal in dependence of the delay time between laser shot and first microwave pulse) with 8-phase cycling routine

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5.1.3 Editor Key bindings

key description key descriptionj cursor left l cursor righti cursor up , cursor downh word left j word righto page up . page downu scroll up m scroll downk begin / end line x exchange wordb insert character n b insert n charactersg go to ? help

5.1.4 OS/9 CommandsPress "F1" to change to the OS/9 command shell while the spectrometer control window is active.

command descriptionmakdir name create directoryrmdir name delete directorycopy name dir_name copy filecopy name_mask –w=/dir_name copy several files which fulfilling the mask

conditionsdel name Delete a filedel name_mask delete files which fulfilling the mask conditionscommand descriptionname_mask mask for names like “*.dat” = all files ending with

“.dat”dir list contents of the directorypwd list actual directory

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chd change directroyedt name line editortype name list the contents of a file/h0 directory of the hardrive/pcd0 directory for the floppy disk (PC, 1.44 MB)

5.1.5 Time Schedule every month: - check phase of the pulse channels

- check water level of heat exchanger every six month: - check ion exchanger of the heat exchanger

- perform signal-to-noise test and compare with old spectra - measure the ringing

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5.2 Sample Spectra

5.2.1 DPPH (one pulse sequence)

On Resonance

Conditions: microwave power = 6 dB, receiver gain = 36 dB, bandwidth = 200 MHz, f = 9.63 GHz, center field = 3423.4 G, d0 = 286 ns, program = fidCYCLOPS (4-phase cycling), p0 = 16 ns, 20 averages per cycle, 1024 points, oscilloscope = 0.2 V/div and 0.2 s/div, Fourier transformation were performed by using LPSVD method (using dead_time module assuming 60 points for the dead time)

60

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left figure: real (upper trace) and imaginary (lower trace) of the FIDright figure: spectra of the left FIDs after LPSVD and FFT

Off Resonance (10 G)

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Conditions: microwave power = 6 dB, receiver gain = 36 dB, bandwidth = 200 MHz, f = 9.63 GHz, center field = 3413.4 G, d0 = 286 ns, program = fidCYCLOPS (4-phase cycling), p0 = 16 ns, 20 averages per cycle, 1024 points, oscilloscope = 0.2 V/div and 0.2 s/div, Fourier transformation were performed by using LPSVD method (using dead_time module assuming 60 points for the dead time)

-120

-100

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106

-100 -50 0 50 100f / MHz

left figure: real (upper trace) and imaginary (lower trace) of the FIDright figure: spectra of the left FIDs after LPSVD and FFT

The spike at 0 MHz is a typical result of an offset in the FID signal (in the real or imaginary part) and is nearly unavoidable. The offset depends on the quality of the phasing (see section 3.1) and the video amplifier.

5.2.2 Coal (two pulse sequence, electron spin echo)

On Resonance

Conditions: microwave power = 6 dB, receiver gain = 30 dB, bandwidth = 200 MHz, f = 9.63 GHz, center field = 3422 G, d0 = 40 ns, d1 = 120 ns, program = echo_fullcycle (8-phase cycling), p0 = 16 ns, p1 = 24 ns, 50 averages per cycle, 1024 points, oscilloscope = 0.5 V/div and 0.2 s/div, Fourier transformation were performed by after shifting the traces by 103 points

26


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-100 -50 0 50 100field / MHz

left figure: real (upper trace) and imaginary (lower trace) of the ESEright figure: FFT of the left ESE signals after shifting the traces by 103 points

Off resonance (10 G)

Conditions: microwave power = 6 dB, receiver gain = 30 dB, bandwidth = 200 MHz, f = 9.63 GHz, center field = 3412 G, d0 = 40 ns, d1 = 120 ns, program = echo_fullcycle (8-phase cycling), p0 = 16 ns, p1 = 24 ns, 50 averages per cycle, 1024 points, oscilloscope = 0.5 V/div and 0.2 s/div, Fourier transformation were performed by after shifting the traces by 103 points

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-100 -50 0 50 100field / MHz

left figure: real (upper trace) and imaginary (lower trace) of the ESEright figure: FFT of the left ESE signals after shifting the traces by 103 points

27

O

O

O


5.2.3 Irgacure 651

FID Detection

Conditions: 100mg IC651 dissolved in 10 ml 2-propanol, using tubes (3 mm inner diameter), purged with argon for 10 min, microwave power = 2.5 dB, receiver gain = 30 dB, bandwidth = 200 MHz, f = 9.63 GHz, center field = 3416.1 G, d0 = 286 ns, d1 = 896 ns, program = fidCYCLOPSext (4-phase cycling), p0 = 16 ns, 50 averages per cycle, 4096 points, oscilloscope = 0.5 V/div and 1 s/div, Nd-YAG laser @ 355 with 4.4 mJ/pulse

-8

-7

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-50 0 50 f / MHz

left figure: real (upper trace) and imaginary (lower trace) of the FIDright figure: FFT of the FID signals (no corrections)

Electron Spin Echo Detection

Conditions: 100mg IC651 dissolved in 10 ml 2-propanol, using tubes (3 mm inner diameter), purged with argon for 10 min, microwave power = 2.5 dB, receiver gain = 30 dB, bandwidth = 200 MHz, f = 9.63 GHz, center field = 3416.1 G, d0 = 306 ns, d1 = 104 ns, d2 = 896 ns, program = echo_fullcycle_ext (8-phase cycling), p0 = 16 ns, p1 = 24 ns, 50 averages per cycle, 4096 points, oscilloscope = 0.5 V/div and 1 s/div, Nd-YAG laser @ 355 with 4.4 mJ/pulse

28


-150

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1086420 time / s -6

-4

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1000

-50 0 50 f/ MHz

left figure: real (upper trace) and imaginary (lower trace) of the ESEright figure: FFT of the ESE signals

5.2.4 FID Signal with no Sample (ringing)

Conditions: microwave power = 3 dB, receiver gain = 36 dB, bandwidth = 200 MHz, f = 9.63 GHz, center field = 3417 G, d0 = 0 ns, program = fidCYCLOPS (4-phase cycling), p0 = 16 ns, 25 averages per cycle, 1024 points, oscilloscope = 0.5 V/div and 0.5 s/div

29


60

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Further information about baseline problems and analysis of FID / ESE signals can be found in my group meeting talk from November 10, 2000.

5.3 List of Components

System includes the following components: Main system:

ESP 300 console, ER 073 10" Magnet, ESP 380-1010 FT Microwave Bridge (Gunn source). ER 082 7 kW Power Supply (for magnet and console) ER 090 7kW Heat Exchanger (for magnet, power supply and bridge) ER 201 X-Y Analog Recorder ("chart recorder") ER 023M Superheterodyne microprocessor based modulation/detection channel

("signal channel"). Doesn't work for modulation amplitudes ca. < 0.4 G. ER 032M Microprocessor based field controller

30


Data system: ESP 3220 computer with the following boards (on a VME bus): GIP ESP 1600-1024 CPU ESP 1600-1014 Motorola 68040 CPU, 8MB RAM, ethernet. GCP ESP 1600-1023 HGP ESP 1600-1022 Graphics board MBC ESP 1600-1048 Microwave bridge control board ADF ESP 1600-1072 Transient recorder SDI ESP 1600-1078 Fast digitizer used for FT experiments GSI ESP 1600-1030 SIP ESP 1600-1005 PSU ESP 1600-1128 Power supply for all these boards 2GB hard drive Software: OS/9 v. 3.0, ESP 380E v. 3.04

FT Components: ESP 380-1020 Controller ESP 385 Pulse Programmer with the following boards: power supply, interface,

time base, 8 pulse channels (note: controller+pulse programmer together on a special console).

Traveling wave tube (TWT) Amplifier from ASE (Applied Systems Engineering) Two flow cell for low-Q dielectric resonator and two flow cell which can be used

together with Helium Cryostat Additional equipment

ER 4118CF-W1 Helium Cryostat with rectangular bottom, optical window, and holder assembly, for the low-Q dielectric resonator Note: this cryostat CANNOT be used with liquid nitrogen. Has following parts: - He pump (MFG Corp., Benton Harbor, Mich., Model DOA-U192-AA,

4.2A, 115V, 60 Hz) with flow display. - Oxford Instruments ITC 4 temperature controller (cable to connect to the

cryostat is missing - He transfer line, with manual needle valve.

31


ER 4118CV-M Metal, liquid nitrogen dewar for the low-Q dielectric resonator. Also provides RF shielding for FT applications when VT is not used. Does not have optical windows. Can be used up to 40-50 deg. C max.

ER 4112HV Helium Cryostat, to be used with standard (ER 4102ST) and flat cell (ER 4103TM) resonators. Note: CANNOT be used with liquid nitrogen. To be used with the Oxford Instruments ITC 4 temperature controller above.

ER 4111VT Liquid nitrogen VT system (ca. 150C to ca 50C with current resonators, up 700C with special high temperature resonator) with: - ER 4111VT Temperature Control Unit - 10 liter glass dewar, quartz transfer line, liq. nitrogen boiler, nitrogen gas

heater. - Suprasil dewar inserts for standard (ER 4102ST) and flat cell (ER

4103TM) resonators. Also special suprasil dewar insert to be used for high temperature applications to prevent cavity heating.

Suprasil liquid nitrogen finger dewar flasks (2), from Wilmad Glass, Buena, NJ. (WG-853-B-Q Large 150m suprasil finger dewar flask).

Resonators:- Standard cavity ER 4102ST (TE102 mode) with grids for optical access.- Flat cell cavity ER 4103TM (TM110 mode) with larger grids for optical

access.- Flexline low Q dielectric resonator (ER 4118). Mainly for FT

applications, but can also be used for CW. Has grids for optical access. Flow cells:

- two coaxial quartz flow cell (ID = 3mm) can be used together with the helium cryostat and have to be mounted from the top

- two coaxial quartz flow cell can only be used with the FT cavity and have to be mounted from the bottom

- rectangular flat cell (10.5x60x0.3 mm) (Wilmad, WG-812-Q) for standard cavity ER 4102ST and ER 4103TM

- rectangular flat cell (16.9x70x0.3 mm) (Wilmad, WG-813-Q) for flat cell cavity ER 4103TM

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5.4 List of LiteratureThis list is not complete and gives only some suggestions. We have a part of these books in our labs and others can be found in the CU libraries. They are very helpful to understand both theory and praxis (therefore, I also included some NMR books) but they go partly to deep in the topic. At the end you will a list of my favorite books, which were written very clearly and will give a good overview about pulsed EPR. Further literature can be found as citations and in the manual for the spectrometer.

5.4.1 EPR A. Abragam and B. Bleaney Electron Paramagnetic Resonance of Transition Ions,

Dover Publications, New York 1970 J.R. Pilbrow Transition Ion Electron Paramagnetic Resonance, Oxford Science

Publications 1990 J.A. Weil (Ed) Electronic Magnetic Resonance of the Solid State, The Canadian

Society for Chemistry, Ottawa 1987 J.M. Spaeth, J.R. Niklas and R.H. Bartram Structural Analysis of Point Defects in

Solids, Springer Verlag 1992 W.B. Mims Electron Spin Echoes, in "Electron Paramagnetic Resonance", Ed. S.

Geschwind Plenum Press, New York 1972 L. Kevan and R.N. Schwartz Time Domain Electron Spin Resonance, Wiley & Sons

1979 C.P. Keijers, E.L. Reijerse and J. Schmidt Pulsed EPR: A new field of applications,

North Holland 1989 A.J. Hoff (Ed) Advanced EPR: application in biology and biochemistry, Elsevier

1989 L. Kevan and M.K. Bowman (Eds) Modern Pulsed and Continuous Wave Electron

Spin Resonance, Wiley & Sons 1990

33


S.A. Dikanov and Y.D. Tsvetkov Electron Spin Echo Envelope Modulation (ESEEM) Spectroscopy, CRC Press 1992

A. Schweiger Pulsed Electron Spin Resonance Spectroscopy: Basic Principles, Techniques and Examples of Applications, Angewandte Chemie 3 Int. Ed. Engl. 30 (1991) 265 - 292

H. Kurreck, B. Kirste and W. Lubitz Electron Nuclear Double Resonance Spectroscopy of Radicals in Solution, VCH 1988

G.R. Eaton, S.S. Eaton and K. Ohno (Eds) EPR Imaging and In Vivo EPR, CRC Press 1991

G. R. Eaton, S. S. Eaton, K. M. Salikhov Foundations of Modern EPR, World Scientific, 1998

N. M. Atherton Priciples of Electron Spin Resonance, Ellis Horwood Ltd. 1993 J. A. Weil, J. R. Bolton, J. E. Wertz Electron Paramagnetic Resonance, John Wiley

& Sons, 1994 P. B. Ayscough Electron Spin Resonance in Chemistry, Methuen & Co LTD, 1967 A. Ponti and A. Schweiger Echo Phenomena in Electron Paramagnetic Resonance

Spectroscopy, Appl. Magn. Reson. 7, 363 (1994) A. Schweiger Creation and Detection of Coherences and Polarization in Pulsed EPR,

J. Chem. Soc. Faraday Trans., 91(2), 177 (1995) C. Gemperle, G. Aebli, A. Schweiger and R. R. Ernst Phase Cycling in Pulse EPR, J.

Magn. Res. 88, 241 (1990) P. Höfer Distortion-Free Electron-Spin-Echo Envelope-Modulation Spectra of

Disordered Solids Obtained from Two- and Three-Dimensional HYSCORE Experiments, J. Magn. Res. A111, 77 (1994)

G. Jeschke and A. Schweiger Generation and transfer of coherence in electron- nuclear spin systems by non- ideal microwave pulses, Molecular Physics, Vol. 88, No. 2, 355- 383 (1996)

G. Jenschke and A. Schweiger Matched two- pulse electron spin echo envelope modulation spectroscopy, J. Chem. Phys. 105 (6), (1996)

M. Hubrich, G. Jeschke and A. Schweiger The generalized hyperfine sublevel coherence transfer experiment in one and two dimensions, J. Chem. Phys. 104 (6), (1996)

34


J. Seebach, E. C. Hoffmann and A. Schweiger Pulse Schemes Free of Blind Spots and Dead Times for the Measurement of Nuclear Modulation Effects in EPR, J. Magn. Res. A116, 221- 229 (1995)

E. C. Hoffmann, M. Hubrich and A. Schweiger Primary Nuclear Spin Echoes in EPR Induced by Microwave Pulses, J. Magn. Res. A117, 16- 27 (1995)

A. Ponti and A. Schweiger Nuclear coherence- transfer echoes in pulsed EPR, J. Chem. Phys. 102 (13), (1995)

5.4.2 Pulsed ENDOR W. B. Mims Pulsed ENDOR Experiments, Proc. Roy. Soc. 283, 452 (1965) E. R. Davies A New Pulsed ENDOR Technique, Phys. Lett. 47A, 1 (1974) A. E. Stillman and R. N. Schwartz ENDOR Spin-Echo Spectroscopy, Molecular

Physics, 35, 301 (1978) M. Mehring, P. Höfer and A. Grupp Bloch-Siegert shift, Rabi oscillation and spinor

behaviour in pulsed ENDOR experiments, Phys. Rev. A33, 3523 (1986) P. Höfer, A. Grupp and M. Mehring High-resolution time-domain electron-nuclear-

sublevel spectroscopy by pulsed coherence transfer, Phys. Rev. A33, 3519 (1986) M. Mehring, P. Höfer and A. Grupp Pulsed Electron Nuclear Double and Triple

Resonance Schemes, Ber. Bunsenges. Phys. Chem. 91, 1132 (1987) M. Mehring, P. Höfer, H. Käss and A. Grupp Multiple-Quantum ENDOR-

Spectroscopy of Protons in Trans-Polyacetylene, Europhys. Lett. 6, 463 (1988) C. Gemperle, A. Schweiger and R. R. Ernst ESR-Detected Nuclear Transient

Nutations, Chem. Phys. Lett. 145, 1 (1988) C. Bühlmann, A. Schweiger and R. R. Ernst Hyperfine-Selective ENDOR, Chem.

Phys. Lett. 154, 285 (1989) C. Gemperle, O. W. Sorensen and R. R. Ernst Optimized Polarization Transfer in

Pulsed ENDOR Experiments, J. Mag. Res. 87, 502 (1990) H. Thomann and M. Bernardo Pulsed Electron-Nuclear-Electron Triple Resonance

Spectroscopy, Chem. Phys. Lett., 169, 5 (1990) H. Cho Stimulated Echo time-domain Electron Nuclear Double Resonance, J. Chem.

Phys. 94, 2482 (1991)

35


P. E. Doan, C. Fan, C. E. Davoust and B. M. Hoffman A Simple Method for Hyperfine-Selective Heteronuclear Pulsed ENDOR via Proton Suppression, J. Magn. Res. 95, 196 (1991)

C. Gemperle and A. Schweiger Pulsed Electron-Nuclear Double Resonance Methodology, Chem. Rev., 91, 1481 (1991)

C. Fan, P. E. Doan, C. E. Davoust and B. Hoffman Quantitative Studies of Davies Pulsed ENDOR, J. Magn. Res. 98, 62 (1992)

Th. Wacker and A. Schweiger Fourier-transformed hyperfine spectroscopy, Chem. Phys. Lett. 191, 136 (1992)

P.Höfer Multiple Quantum Pulsed ENDOR Spectroscopy by Time Proportional Phase Increment Detection, Appl. Magn. Res. 11, 375- 389 (1996)

5.4.3 NMR Abragam The Principles of Nuclear Magnetic Resonace, Oxford at the Clarendon

Press 1978 R. R. Ernst, G. Bodenhausen and A. Wokaun Principles of Nuclear Magnetic

Resonance in One and Two Dimensions, Oxford science publications 1987 R. Freeman A Handbook of Nuclear Magnetic Resonance, Longman Scientific &

Technical 1987 A. Bax Two Dimensional Nuclear Magnetic Resonance in Liquids, Delft University

Press 1982 M. Mehring Principles of High Resolution NMR in Solids, Springer Verlag1983 E. Fukushima and S.B.W. Roeder Experimental Pulse NMR: a nuts and bolts

approach, Addison-Wesley 1981 D.M.S. Bagguley (Ed) Pulsed Magnetic Resonance: NMR, ESR and Optics, Oxford

Science Publications 1992

5.4.4 My favorite books W.B. Mims Electron Spin Echoes, in "Electron Paramagnetic Resonance", Ed. S.

Geschwind Plenum Press, New York 1972

36


L. Kevan and R.N. Schwartz Time Domain Electron Spin Resonance, Wiley & Sons 1979

C.P. Keijers, E.L. Reijerse and J. Schmidt Pulsed EPR: A new field of applications, North Holland 1989

A. Schweiger Pulsed Electron Spin Resonance Spectroscopy: Basic Principles, Techniques and Examples of Applications, Angewandte Chemie 3 Int. Ed. Engl. 30 (1991) 265 - 292

N. M. Atherton Priciples of Electron Spin Resonance, Ellis Horwood Ltd. 1993 J. A. Weil, J. R. Bolton, J. E. Wertz Electron Paramagnetic Resonance, John Wiley

& Sons, 1994

5.5 Persons at BrukerPlease contact Ralph Weber for all problems related to pulsed EPR. For technical issues (like heat exchanger) you should call Chuck Hanson. Both of them were very helpful in the last two years.

Arthur Heiss, V.P. and EPR Product Manager, EPR Division Bruker Instruments Inc., 19 Fortune Drive, Billerica, MA 01821, USAPhone: 978 - 663 7406, Fax: 978 - 670 8851Email: [email protected]

Ralph Weber, Sr. Applications Scientist, EPR Division Bruker Instruments Inc., 19 Fortune Drive, Billerica, MA 01821, USAPhone: 978 - 663 7406Phone: 978 - 667 9580 ext. 137, Fax: 978 - 670 8851Email: [email protected]

Robert J. Dick, EPR Operations Coordinator, Bruker Instruments, 19 Fortune Drive, Billerica, MA 01821, USAPhone: 978 - 663 7406Phone: 978 - 667 9580 ext. 128, Fax: 978 - 670 8851

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Email: [email protected]

Donald Kwet, Senior Service Engineer, EPR Division Bruker Instruments Inc., 19 Fortune Drive, Billerica, MA 01821, USAPhone: 978 - 663 7406Phone: 978 - 667 9580 ext. 125, Fax: 978 - 670 8851Email: [email protected]

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Chuck Hanson, Service Engineer, EPR Division Bruker Instruments Inc., 19 Fortune Drive, Billerica, MA 01821, USAPhone: 978 - 663 7406Phone: 978 - 667 9580 ext. 288, Fax: 978 - 670 8851Email: [email protected]

5.6 FlexLine Manual

39

Documents

Operating the ESP380E - Columbia Universityturroserver.chem.columbia.edu/PDF_db/FT-EPR Instructions.doc · Web viewSolution: The heat exchanger is not running in most of such cases