Active Electric Shims

• 1: Installation
• 2: Specifications

Welcome to the online documentation of the Bridge12 Active Electric Shims (AES) for electromagnets.

The Bridge12 AES can be installed in an electromagnet with horizontal field orientation, commonly used in EPR spectroscopy. In total 5 different coils are included to actively control the Z1, Z2, X, and Y gradients. In addition a B0 (Z0) coil is integrated to perform small field adjustments.

Please follow the installation and operation instructions. If you have further questions please contact Bridge12 at support@bridge12.com.

1 - Installation

Before You Start …

What is Included

The Bridge12 AES come by default with the following parts (see figure below):

1. Electrical Shims (right side, qty.: 1)
2. Electrical Shims (left side, qty.: 1)
3. Shim spacers (qty.: 4)
4. Shim supports (qty.: 8)
5. Adjustment/tightening tool (qty.: 1)
6. Cables to connect shims to shim interface (qty.: 2)
7. Shim interface (qty.: 1)
8. Shim board adapter for Bruker BSMS shim power supply (qty.: 1)
9. Cable to connect shim interface (7) to Bruker BSMS shim board adapter

Assembling the Shims

The electrical shims are supported between the magnet poles using a total of 8 shim supports and 4 shim spacers (shown in figure below).

To assemble the shims:

1. Place the electrical shims (1 and 2) at the side of the magnet. The board labeled “left” should face the left magnet pole. The board labeled “right” should face the right magnet pole. The labels are located on the back of the boards.
2. Place the shim spacer between the shim boards
3. Screw in the shim supports on both side.

The assembly should look similar to the assembly shown in the figure below.

4. Repeat the previous step for all shim supports and spacers.

Alternatively, you can first assemble the shim boards using the supports and the spacers outside the magnet and place the assembled shims between the magnet poles.

Under some circumstances it is not possible to use all 8 shim supports. In this case two supports can be omitted and replaced by two screws as shown in the following image. However, make sure when locking the shims in place that their position is fully secured and that the shims won’t slide down. We don’t recommend removing more than one set of shim supports.

Locking the Shims in Place

Once you have assembled the shims and placed between the magnet pole pieces, you need to lock the shims in place. Each support of the shims has an adjustment screw and a counter nut (see figure below). Before you start turn the counter nut to face the screw as shown in the figure below.

To hold the shims between the magnet poles, turn the adjustment screws on all sides, until they touch the side of the magnet. Make sure the shims are centered between the pole pieces of the magnet. To turn the screws, especially when the tops of the screws are close to the sides of the magnet use the Adjustment/Tightening tool.

Once the shims are supported between the magnet poles, lock the adjustment screws by turning the counter nut until it touches the shim support. Make sure the nut is not overtightened.

The picture below shows the shims installed in an electromagnet for EPR spectroscopy.

Connecting the Shims

To use the shims, the following connections have to be made:

1. Shims to shim interface
2. Shim interface to shim power supply

To connect the shims to the shim interface follow these steps:

1. Starting with the shims located to the right, connect the ribbon cable marked “RIGHT” to the right shim board.
2. Connect the same ribbon cable the shim interface.
3. Repeat the step for the ribbon cable marked “LEFT”.

Connecting the Shims to a Lab Power Supply

The shims can be operated using any benchtop lab power supply. For convenience a multi-channel power supply can be used. Often these power supplies are not bi-polar, in which case you need to swap the leads of the respective channel if you would like to reverse the gradient (e.g. Z1 to -Z1). The power supply can be directly connected to the 15 pin sub-D connector of the shim interface.

Connecting the Shims to a Shim Power Supply

The shims can be operated using a shim power supply e.g. of a NMR spectrometer. The following instructions are specific to a shim power supply used in Bruker NMR consoles (courtesy to Prof. Song-I Han, UCSB).

To connect the shims to a Bruker shim power supply (e.g. BSMS/2) follow this steps:

1. Connect the shim board adapter to the the shim power supply (see image below, left).
2. Connect the 15 pin sub-D cable to the shim interface.
3. Connect the 15 pin sub-D cable to the shim board adapter.

Once you have made these connection, the shim can be controlled through the shim power supply.

If you need help at any step of the installation please contact Bridge12 at support@bridge12.com.

2 - Specifications

The Bridge12 Active Electric Shims (AES) are a 5 channel shim system for electromagnet with a horizontal field. These magnets are typically used in Electron Paramagnetic Resonance (EPR) spectroscopy. The five channels or the shims are: Z0 (or B0), Z1, Z2, X, and Y. Each channel can operate at a current of up to 1.5 A.

Shim Interface Pinout

If you need help at any step of the installation please contact Bridge12 at support@bridge12.com.