2024年3月28日发(作者：sogou搜狗输入法官网)

Physical Property Measurement System (PPMS) – AC Transport (ACT)

All users must receive specific training for the AC Transport option regardless of training on other options. Reserve all

necessary time in Coral and enable and disable when starting and finishing your experiment. Fill out a log sheet for each

use.

The AC transport option can used for making several different measurements with AC excitation: resistivity, I-V curves,

Hall Effect, and critical current. Resistance measurements can also be made using the Resistivity option. Which option is

more appropriate depends on several factors, including whether an AC signal is desirable/acceptable, the resistance of

the device(s) to be tested, and the number of devices to be tested. Consult the system documentation and/or facility

staff to help determine which option is appropriate. The three “transport…” PDF documents on the PPMS computer

desktop are a particularly useful resource for making electronic transport measurements.

Sample Preparation

The AC Transport option performs measurements using 4 or 5 contact points on up to 2 channels at a time. The

standard ACT puck (see right) includes pre-mapped pads I+, I-, V

A

+, V

B

+, and V- on both

Channels 1 & 2. The recessed area measures 10.8 mm square (with rounded corners), so

samples that fit within this area will work best. The base is conducting, so an insulating layer

such as Kapton tape will be necessary for samples with conductive back sides. Electrical

contact between the sample and the desired channel input pads can be made via wire

bonding, soldered or silver-painted wires, spring-loaded press contacts (consult staff on use

of these), or other methods. Alternatively, samples can be mounted on the user puck, which

has a blank face and no pre-configured channel set-up. This can be useful for larger samples

or if no ACT pucks are available. The pin-to-channel correspondence for the user puck is

posted on the bulletin board. The ACT or user puck can be used in combination with the User Bridge (the blue face plate

corresponds to the ACT option channels) to test sample-to-puck connections in advance of insertion into the PPMS using

a hand-held ohm meter or other device.

Activation

1. In the MultiVu software, de-activate any other active option, and physically remove the cables/hardware as

necessary according to the respective SOP.

2. Click Utilities – Activate Option… and open the ACT connection diagram and connect all cables

accordingly. Note that if the ACMS option has been used more recently than the AC Transport option (check the

log book to determine this if necessary), two cables on the back of the Model 6000 controller will need to be

changed.

3. Select and activate the AC Transport option. will pop up to indicate the activation status.

4. If not immediately inserting a sample, insert the baffle/flange rod and clamp it in place, then purge and seal the

system (note – this is not necessary if switching from the Resistivity option). Or, go to step 3 under

Measurement Procedure to install a sample.

Measurement Procedure

Refer to Chapter 5 of the AC Transport manual for information on performing measurements. Once the option is

activated, the tabbed AC Transport Control Center contains most commands needed to set up and perform a

measurement. To insert a sample:

1. On the Install tab, click the Vent button and follow the on-screen instructions.

2. When the system is vented, remove the baffle/flange rod.

3. Visually verify that there is not a puck in the system, and if there is, remove it.

4. To place the puck in the puck insertion tool:

a. Flip the switch on the handle up to open the collar.

b. Put the puck into the bottom of the tool, sample side first.

c. Hold the puck in place while flipping the switch down to lock the puck in place.

5. Using the tool, slowly lower the puck into the probe. When it reaches the bottom, rotate it until the key aligns

with the key slot (this happens with the key facing forward), then press down to engage the pins.

6. Flip the switch on the tool up and withdraw the tool.

7. Replace the baffle/flange rod and finish the install procedure in the software to purge and seal the system.

8. Place the puck insertion tool back on the wire shelving unit.

9. On the Data File tab, click Browse and set up a file location and name. Then, you will be prompted to enter

sample info on the Sample 1 and Sample 2 tabs; click Next >> and Finish after each one, respectively.

All measurements made using AC Transport fall under one of four modes corresponding to the four buttons which are

always visible at the bottom of the AC Transport Control Center (regardless of which tab is open): Hall

Coefficient, Resistivity, IV Curve, or Critical Current. Clicking one of these buttons will

open a new window which serves as the interface for that measurement. Since each interface and measurement

procedure is unique, users should refer to the relevant sub-section of section 5.3 of the AC Transport manual for specific

information on a measurement type. In general:

Immediate measurements can be made by clicking the Measure button at the bottom of the measurement

window. Results are displayed and can be saved to the specified file (see above) by clicking Save.

Within the AC Transport Control Center, the Waveforms tab displays the expected and actual data waveforms

for every measurement. This can be useful for seeing noise levels and determining if the input parameters and

measurement range are appropriate.

For information on setting up and running sequences, refer to the PPMS general instructions. ACT

measurement commands are listed under “AC Transport” (click the + to expand the list of choices). When a

measurement command is selected, the measurement interface includes tabs for Sample 1 and Sample 2; the

measurement can be made on either or both samples (each with their own separate parameters) by clicking the

respective Measure check-boxes, whereas one or the other is selected in an immediate measurement. The

PPMS Data tab allows the user to select what parameters and results (from both the measurement and the

system hardware) will be saved to the file.

To change samples, set the system temperature to 300 K and the magnetic field to 0 Oe (persistent); this should be done

at the end of each sequence, but can be done manually if necessary. Use the sample change sequence as described

above (with slight differences for puck removal). When finished, the AC Transport option can be left active in the

system.

De-activation and Removal

1. Set the system temperature to 300 K and the magnetic field to 0 Oe (persistent).

2. Click Utilities – Activate Option… and select and de-activate the AC Transport option.

3. Remove the AC Transport LEMO connector from the back of the probe and, if necessary, the connectors from

the back of the Model 6000 controller. Hang the LEMO connector from one of the hooks on the wall.