SpecMan4EPR

• 1: Overview
• 2: Installation
• 3: Configuration
• 4: Magnet Control
• 4.1: Superconducting Magnets
• 4.1.1: SpecMan Magnet Control GUI
• 4.1.2: Heater Control
• 4.1.3: Operating the Magnet
• 5: Troubleshooting
• 5.1: SpecMan4EPR
• 5.2: Magnet

1 - Overview

SpecMan4EPR is a highly flexible platform to control spectrometers. The software can work with a large variety of commercial equipment such as AWGs, digitizers, lock-in amplifiers, etc., but also home-built components.

The software features:

• Simple to use Graphical User Interface (GUI), so even non-expert users can setup complex experiments.
• Visualization of pulse sequences including all triggers.
• A powerful AWG engine for modern EPR experiments. The software comes with many different predefined pulse shapes (e.g. Chirp-Pulse, WURST-Pulse, etc.) but also allows for convenient upload of user specified pulse sequences.
• Flexibility to sweep variables. Almost every parameter can be defined as an axis in SpecMan4EPR and can be varied.
• Integrated magnetic field control for superconducting magnets.

2 - Installation

Software Installation

Typically, your Bridge12 EPR spectrometer comes pre-installed with SpecMan4EPR and the system is already configured depending on your needs and the available hardware. This includes all hardware drivers and any additional software that is required to operate the spectrometer.

SpecMan4EPR is not free and a licensed is required to run the software. This license file depends on the computer hardware and can not just simply transferred to a new computer. If you change the hardware, you may have to obtain a new license file to activate the software. To bet a new license file, please follow the instructions in the Troubleshooting Section

3 - Configuration

Typically, your EPR spectrometer will be delivered with a pre-configure version of SpecMan4EPR. Below, we provide a sample configuration. However, the exact values for certain parameters (e.g. COM port) may differ from system to system.

Device Configuration

To configure the different hardware component in SpecMan4EPR, open the Device Panel by clicking on the button labeled Configuration of devices (see button indicated by red box in figure below).

Once you click the button the Device Configuration window will open.

When you first open the Device Configuration window, you will be in Basic Access mode. In this mode, you can only view the parameters but you won’t be able to change any parameters or safe a new configuration. For this you need to access the Expert Mode. In the Basic Access mode, the safe and load buttons are greyed out.

To access the Expert Mode click Expert Access button to the top right of the window. You will be prompted with a password window. Simply acknowledge the password in the window by pressing the OK button. The Device Configuration window will change to Expert Mode (see figure below).

EPR Bridge

Bridge12 B12TXIF bridge controller and LabJackT7 (B12TXIF)
Driver version: 3.5

Interface 0: LabJack
Interface 1: Pixel controller

Name: BRIDGE

A sample configuration is shown below.

Microwave Source

Synth HD ver. 2.0 (SYNTHHD) Driver ver. 2.0

Name: SRC

A sample configuration is shown below.

Digitizer

The configuration of the digitizer depends on the model and make you are using. Please contact support@bridge12.com for more information.

Arbitrary Waveform Generator (AWG)

The configuration of the arbitrary waveform generator (AWG) depends on the model and make you are using. Please contact support@bridge12.com for more information.

SpecMan4EPR Options

Please use the default SpecMan4EPR parameters for Directories and files. To access this go to Configuration and Select Options and expand the Directories and files menu.

4 - Magnet Control

Two types of magnets are commonly used in EPR spectroscopy:

1. H-Frame Electromagnets
2. Superconducting Magnets

Most Bridge12 EPR spectrometers are equipped with a superconducting magnet. Both magnet types can be controlled through SpecMan4EPR.

4.1 - Superconducting Magnets

Overview

Superconducting magnets used in Bridge12 EPR spectrometers come with an integrated heater switch so the magnet can be operated in a driven-mode or in persistent mode. If the magnet switch is closed, the magnet is in persistent mode, similar to superconducting magnets. While the magnet will have the lowest drift rate in persistent mode, generating a very stable field, the field can not be swept/changed. To sweep the magnetic field, the heater has to be activated to open the switch.

A typical scenario to put the magnet in persisten mode at e.g. 5 T would look like this:

1. Assuming the magnet is at 0 T activate the heater to open the (superconducting) switch. Wait until the heater reaches its target temperature (about 11 K).
2. Ramp the field to the desired value, here 5 T. During ramping the field the magnet voltage will increase.
3. Wait for the field to settle. This is indicated by the lowest voltage read by the power supply. When the magnet is at field, the voltage will never be 0 V, since this voltage also includes the voltage drop across the magnet leads.
4. Deactivate the heater to close the switch. Wait for the heater to return to its base temperature.
5. Ramp down the current in the magnet leads.

At the end of this procedure this the magnet is in a 5 T persistent field state and the drift will be very low. To change the field, first the magnet leads need to be ramped up to match the current in the magnet.

4.1.1 - SpecMan Magnet Control GUI

The superconducting magnet can be completely controlled through the SpecMan4EPR software using the. From the SpecMan magnet GUI the user can activate the heater switches, move/sweep the magnet field, and can put the magnet in persistent mode.

Launching the Magnet GUI

To launch the magnet GUI:

1. Go to the DDI menu
2. Select Set Field from, FLD from the menu. This will open a separate window with all magnet controls.

The following window will appear:

The magnet control window has three different buttons to select the functionality:

1. Heater Control: Click this button to access the heater controls to enable/disable the heater switch (see figure above, left).
2. Field Control: Click this button to access the field controls to change/set the magnetic field strength (see figure above, right).
3. Polarity Control: Click this button to change the polarity of the magnetic field (currently not used) (not shown/used).

4.1.2 - Heater Control

To change the magnetic field first the superconducting heater needs to be activated. This will connect the magnet power supply to the main coil and will allow the user to increase or decrease the current in the main coil and therefore moving the magnetic field.

The value of the magnetic field is shown in two different colors, depending if the heater switch is activated or not:

• Yellow : The heater switch is off. If the field is at a value of 0 T, the main coil is completely discharged. If the value is not 0 T it means the magnet is in persistent mode, and the field is “parked” at that value. Before activating the switch, the current in the magnet leads not to ramped back to the persistent mode value (see figure above, left).
• Green : The heater switch is activated (on) and the field can be moved (see figure above right).

Operating the Switch

Opening the Switch at 0 T

To open the superconducting switch:

1. If the magnetic field is at a value of 0 T, click the icon to open the switch in the magnet GUI (see figure above, left).
2. Confirm that you want to open the switch by clicking Yes in the dialog box.
3. Wait for 10 - 20 seconds for the switch to fully open.

Opening the Switch when Magnetic Field is not at 0 T

To open the superconducting switch:

1. Enter the value of the persistent field to charge the current in the leads to match the current when the switch was closed.
2. Wait for the power supply to reach the field.
3. Click the icon to open the switch in the magnet GUI (see figure above, left).
4. Confirm that you want to open the switch by clicking Yes in the dialog box.
5. Wait for 10 - 20 seconds for the switch to fully open.

Closing the Switch

To close the superconducting switch:

1. Click the icon to close the switch in the magnet GUI (see figure above, right).
2. Wait about 10 - 20 seconds for the switch to close

4.1.3 - Operating the Magnet

Depending on the type of experiment the magnet field is either:

1. Moving For example in a echo-detected field-sweep experiment. Here, the field is swept while recording the echo intensity.
2. Static For example in a DEER/PELDOR experiment. These type of experiments are performed at a static magnetic field value. If the user does not change the field for a long time (e.g. an overnight experiment), it is recommended to put the magnet in persistent mode.

Typically, when switching on the spectrometer, the user would set a field value close the start value. This is not strictly required but will speed up operations when the field is moved a lot during an experiment session.

Once an initial value is set the field is entirely controled by SpecMan4EPR.

Setting an Initial Field Value

To prepare for an experiment:

1. Open the SpecMan4EPR Magnetic Field GUI.
2. Click on the heater control icon.
3. Activate the superconducting heater switch. After you clicked the icon to activate the switch wait for about 10 - 20 s for the switch to completely open.
4. Click the icon to control the magnetic field.
5. Enter the desired value for the magnetic field and press the ENTER key.
6. Wait for the magnet power supply to reach the desired magnetic field value.
7. (Optional) If the EPR experiments are performed at a static magnetic field, close the superconducting magnet switch to put the magnet in persistent mode. Enter a value of 0 T for the magnetic field to ramp down the current in the magnet leads.

Ramping Down the Magnet

It is completely fine to leave the magnet at field, if the spectrometer is not used for a short time. However, if the spectrometer is not used for a while, the magnetic field should be discharged. To ramp down the magnet:

1. (Optional) If the magnet is in persistent mode:
   1. Enter the field value, matching the magnetic field value of the magnet and hit the ENTER key.
   2. Wait for the power supply to reach the value.
   3. Open the superconducting magnet switch. After you clicked the icon to activate the switch wait for about 10 - 20 s for the switch to completely open.
2. Enter a value of 0 T for the magnetic field strength and hit the ENTER key.
3. Wait for the magnet to reach a field of 0 T.
4. Once the magnet reached 0 T, close the superconducting magnet switch.

Changing the Ramp Rate

When sweeping or changing the magnetic field, the rate, at which the magnetic field is changed, can not exceed a specific value. This value for the sweep rate is given by the magnet manufacturer. It is common for superconducting magnets to have different sweep rates for different field value regimes.

5 - Troubleshooting

5.1 - SpecMan4EPR

Software Installation

Re-Installing SpecMan4EPR

Debugging

Debugging the LabJack Interface

Software Installation

Re-Installing SpecMan4EPR on new Hardware

In case have to re-install SpecMan4EPR on a new computer, follow these steps (assuming you saved a previous copy of SpecMan4EPR):

1. Start by creating two folders in the main directory (C:).
   1. C:\SpecMan4EPR
   2. C:\SpecManData
2. Copy the SpecMan4EPR application (SpecMan4EPR.exe) into the application directory (C:\SpecMan4EPR)
3. Inside the SpecMan4EPR folder create three subfolders:
   1. cfg - to store configuration files
   2. pattern - to store pattern files
   3. tpl - to store pulse program templates
4. Double click the SpecMan4EPR icon to start the application. Since no license is installed, SpecMan4EPR will create a LIF File. To obtain a license please send this file to support@bridge12.com and include any additional information about your spectrometer (e.g. serial number)
5. You will receive a license file (Specman4EPR.nlic). Move this file into the SpecMan4EPR directory. This will activate your software license and you will be able to use SpecMan4EPR.

Debugging

Serial Communication

Serial communication in SpecMan4EPR is most conveniently debugged in the built-in script editor.

LabJack DAQ Interface

To debug communication with the LabJack interface and to enable the verbose mode for the LabJack interface follow these steps:

1. In SpecMan4EPR to the the Script tab
2. Select the LABJACK interface from the dropdown menu
3. Select S00
4. From the command dropdown menu select .echo
5. Enter 1 in the empty text box
6. Hit ENTER.

Once the verbose mode is enabled, open the Log Window by clicking the View log window in the toolbar to the right. For clarity, you can clear the log by right clicking with the mouse into the window and click Clean Log. This will clear all old messages.

5.2 - Magnet

Magnet Control

Recovering after Magnet Quench

Recovering after Magnet Quench

A magnet quench can occur for several reasons, such as sudden loss of electricity, or the cooling water supply shuts down. If the helium compressor shuts off while the magnet coils are charged, or are in persisten mode, the user has about 8 minutes left until the magnet coils have reached about 8 K and the magnet will quench. However, in contrast to a wet magnet, this is rather uneventful. The temperatures of all sensors will suddenly increase. Once electricity (or cooling water) is back, the helium compressor will restart automatically and the magnet will be cooled. If the compressor doesn’t restart automatically, it has to be done manually.

Once the magnet has reached its base temperature it is again safe to operate the system. The temperatures can be observed either directly on the temperature monitor or through the systems logger. Typical temperatures are:

To energize the magnet again follow these steps:

1. Make sure the helium compressor is running and that the magnet has reached its base temperatures (see table above).
2. The power supply may show the message HEATER switched off at XX.XXX Amps. This indicates, the magnet was in persistent mode when the quench occurred. However, the user can safely ignore this message. To clear this message:
   1. If the power supply is in remote control mode, take the power supply back into local front panel operation mode by pressing the button labeled REMOTE.
   2. Press the HEATER button to activate the switch (the LED light will come on). Wait for a few seconds.
   3. Press the HEATER button again to switch the heater off.

Alternatively, the user can just restart SpecMan4EPR and start using the magnet.