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===== MPMS-5S manual =====


(version 1.4, 22-06-2007)


===== Requirements to ALL users =====


1) Every user is REQUIRED to report any problem that appears during the measurements. If there is a hardware problem write it (in understandable English) in the logbook; next to the MPMS and report it as soon as possible.
2) Every user is REQUIRED to start a new log file at the beginning of his measurement day. If the measurements are performed by the same user in successive days only one file is enough. The files should be saved in the directory. 

3) The samples should always by loaded or taken out at 300 K in order to avoid o-ring leaks. 

4) After you perform your experiment set instrument at T = 300 K, B = 0 T as a courtesy to the next user, or if the equipment will not be used for some time, after removal of the sample at 300K, switch to standby mode.




===== Measurement tips =====


1) Whenever you want to set a low temperature (< 20 K) and you are at temperatures above 100 K, set first the temperature at 20 K, wait until is stable and only then proceed with the desired temperature set point. 

2) If it happens that the system is extremely slow in stabilizing low temperatures (< 20 K), i.e. it takes hours to get the required temperature, or it is clear that the temperature will not be stable, try to set the temperature at 20 K, wait until is stable and then try again. 

3) (i)If there are problems in cooling from 300K (sometimes this can be very slow, of the order of 5 hours to get to 20K), then it is possible to manually override the PID regulation and cooling power. (Obviously use with caution, although this seems to be reset by the software everytime you change the set-point: this is probably part of the problem). (ii) Go into Utilities→Diagnostics→Drivers Channels. Look at Driver 2, the Max. Power will be probably set to 8mW/Ohm (top right) and the output power will probably be at this maximum (middle top). At the bottom you can change the output maximum, try something like 9 or 10mW/Ohm. It should now cool faster (although remember this value will be reset when either you run a sequence with a T scan, or change the T setpoint with this window closed). 

4) It is wise to use “NO Autotrack” in combination with “linear regression” in the MPMS if one has a small signal that becomes small during the measurement. Remember, if the iterative procedure makes a mistake once with the center position, the rest of the measurement is probably worthless. 

5) Always check the results of the measurements looking in the RAW data file. One should check whether the measured signal has a dipole shape 

6) When performing very sensitive measurements at low magnetic fields one should be aware that a remnant field of the order of up to 50 Oe could be stored in the magnet. In order to get rid of that one can use the RESET THE MAGNET option or the DEGAUSS option (please read the manual!!!). DO NOT ABUSE these options. Please note that repeating them too often can seriously damage the magnet. Therefore, every single time you perform such a procedure make a note in the logbook. 

7) When centering the sample for the first time one should always try to use the Full DC scan option to determine which other signals can perturb the measurements. 

8) When applying the magnetic field for most of the experiments is better to use the No Overshoot Mode. 

9) The samples you would like to measure should not be wider than 6 mm and longer than 1-2 mm. 

10) Some Notes on temperature settings:

Setting the temperature is fairly straightforward. But, the time to equilibrate different temperatures varies. The change from 300°K to 35°K takes 20 minutes, whereas going from 35°K to 5°K takes 10 minutes. It is good practice to let the system stabilize at 35 K for at least 20 min. As it reaches the set temperature, the temperature will cycle above and below the final temperature with decreasing amplitude until it stabilizes at the set temperature. To achieve a temperature below 4.2°K the system has to perform several manipulations, and the time required to stabilize is longer. It is not necessary, but it is recommended before beginning any work below 4.2°K, stabilize the temperature at a value between 5°K and 10°K. When the temperature is set at a value below 4.2°K the system will first transfer some liquid Helium into a special chamber. This step takes 12 minutes. Then, to lower the temperature below 4.2°K a partial vacuum is pumped on the special chamber. Overall, this process will take 15 to 20 minutes. Patience is a necessity here, since resetting the temperature during the process will just restart the time required. On occasion the system will not stabilize at the set temperature. If the temperature just seems to be bouncing around the final temperature, and the amplitude of the cycling is not decreasing, then try typing in the temperature again. When trying to go below 4.2°K, if the temperature settles at a value above 4.2°K after 20 minutes, then try typing in the temperature again. When the liquid Helium level drops below 40% working at lower temperatures will take longer; and, working below 4.2°K is not possible.

===== Principle of operation =====

The MPMS consists of an instrument station, a control/electronics rack/station, a computer a sample holder rod, various small tools, and supplies. 

1. Principles of operation: The MPMS 5S is a commercial SQUID (Superconducting Quantum Interference Device) magnetometer that measures the magnetic moment of a sample at a controlled temperature (between 1.7 K and 400 K) in an applied magnetic field (up to 5 tesla). Most operation steps are performed through a userfriendly, menu-driven software package that runs on a personal computer, which interfaces to the electronic equipment that drives the hardware. The operation of this machine can be broken down into various parts: sample transport, temperature (T) control and gas handling system, magnetic field (H) control, and signal detection electronics. 
The details can be found in the fairly comprehensive manuals provided by QD, but the basic principle of operation is as follows. The sample is dragged through superconducting (SC) pickup coils, which are wound in a second derivative arrangement. Magnetic flux that passes through a SC coil will induce a persistent current in the coils. This current drives a separated small SC coil, which produces a magnetic field that is sensed by the SQUID. In conjunction with the RF circuitry, the SQUID acts as a magnetic flux transducer, producing an output voltage signal proportional to the magnetic moment m that produced the flux. The absolute value of m can be calibrated by measuring a standard sample of known moment (such as Pt or Pd). By cycling the sample through a second derivative coil arrangement, contributions from electronic drift are greatly reduced, as are any constant external field (such as the earth’s magnetic field) and any constant gradient field contributions. A stepping motor raises the sample from below the pickup coils, to above them, and the voltage is digitally recorded at a specified number of intervals as the sample passes through the coils. Due to the second derivative arrangement, a plot of voltage vs height yields a characteristic shape (see figure in the User’s manual). The center peak occurs at the center of the coil arrangement that consists of 2 windings wound in the positive sense. Each of the two minima on either side of the center peak occurs near a single winding, wound in the negative sense and placed in series with the center windings. The total voltage is the sum of the flux contributions from each winding. The measured “scan” is then fit to a theoretical curve for an ideal dipole moment to determine the magnetic moment of the sample. Samples that are long compared to the pickup coil diameter (1 cm) will yield an error in the calculated moment. Samples that are not spherical will have higher multipole moments. You should convince yourself that a second derivative coil type arrangement will not give a voltage for a uniform field and/or constant gradient field. 
During the measurements, the sample tube (9 mm ID) contains ~ 2 torr (1 atm. = 760 torr) of He exchange gas, providing good thermal contact with the outer cooling annulus. The cooling annulus is cooled by cold (~4.5 K) He gas flowing through it from the bottom. The power to a resistance heater is altered to control the temperature at a constant value. The temperature is measured by a four-wire ac resistance technique using either a platinum resistor (T > 40 K) or a germanium resistor (T < 40 K), which are isolated from the magnetic field due to the SC magnet, but still are in good thermal contact with the sample tube. To reach temperatures below 4.5 K, liquid He (LHe) is collected at the bottom of the cooling annulus and subsequently pumped by the mechanical pump, which reduces the helium vapor pressure and therefore the boiling point of the LHe. There is a vacuum space surrounding the cooling annulus, which isolates it from the LHe bath (dewar) which keeps the entire cryostat (insert) cold, including the superconducting magnet. An outer vacuum jacket isolates the LHe bath from room temperature, and is superinsulated with aluminized mylar which acts as a thermal shield. The superconducting magnet is wound in the shape of a solenoid and can attain fields as high as 7 tesla (70,000 gauss). 
The field is sufficiently uniform only in a small region about the center of the pickup coils. Field homogeneity is of particular concern when cycling hysteretic superconducting samples. The magnet is energized by a 50 amp power supply. When the desired current to the magnet is reached, the “persistent switch” is closed; that is, the magnet is short circuited by a SC wire, and the power supply current is ramped down. The current in the magnet is maintained because of its zero resistance and high inductance (~5 henries). Special care must be taken with SC magnets to prevent a “quench”. If any part of the SC magnet goes into the normal state (due, for example, to an insufficient amount of LHe in the dewar), creating a region of finite resistance, the high current will generate more heat and the entire magnet will be driven into the normal state in a small amount of time. The current will then decay to zero and, due to the large inductance of the magnet, large voltages on the order of kV can potentially be induced across the windings of the magnet. This can cause arcing and destruction of the expensive magnet. There are, however, protective diodes across the magnet that should limit the voltage to a safe value. In any case, a large amount of expensive LHe will evaporate very quickly. To prevent a quench, you should not exceed the recommended maximum field for the various levels of LHe. Above 50%, you can go to the maximum value of 7 T. You should also program each run to ramp the field to zero at the end. 


===== Basic operation: =====


a. Check the LHe level to make sure you can reach the fields you need: 

LHe level (%)  Maximum field  
more than 50%  50 kOe, 5 T  
30-50%  10 kOe, 1 T  
< 30%  no field  


Normally, if the level is below 50%, helium transfer is needed. Please refill the cryostat!!! Do not apply a field greater than the above specified limits, or the magnet could quench, potentially causing irreparable damage to the SQUID. 

b. Log into the lab notebook and record: 

1. Your name. 

2. Filename. 

3. Liquid helium level. (It automatically updates) 

4. Max field you will apply. Indicate if you demagnetize the magnet by oscillating the field to zero from a high value > 5 kOe. 

5. Sample being measured - its chemical formula and code which identifies it. 

6. Any unusual behavior. 

b. Mount the sample: When making magnetic measurements, you should be aware that virtually every solid material has a finite magnetic susceptibility, although some are larger than others. The sample holders will contribute to your signal, impurities within and on the surface of your sample will also contribute. At the very least there is a small Landau diamagnetism; metals also have Pauli paramagnetism. Of special concern are paramagnetic or even ferromagnetic impurity contributions, which become large at low temperatures. Therefore you should handle samples and sample holders with gloves and keep them clean. Measurements of samples with small moments are often difficult because of these other contributions. Place the sample in a gelatin capsule with some cotton or a kimwipe piece to hold it in place. To prevent it from opening while purging, puncture a small hole in the top of the capsule with a needle or scalpel. The gel cap is then inserted into the center of a straw and held in place with 2 small pieces of a similar straw. The magnetization due to a uniform rod which is longer than the span of the pickup coils (such as the straw) will produce a constant flux, and does not contribute to the calculated magnetic moment. 



===== sample preparation =====


A) drinking straw holder

1) Prepare the sample for the drinking straw holder: When making magnetic measurements, you should be aware that virtually every solid material has a finite magnetic susceptibility, although some are larger than others. The sample holders will contribute to your signal, impurities within and on the surface of your sample will also contribute. At the very least there is a small Landau diamagnetism; metals also have Pauli paramagnetism. Of special concern are paramagnetic or even ferromagnetic impurity contributions, which become large at low temperatures. Therefore you should handle samples and sample holders with gloves and keep them clean. Measurements of samples with small moments are often difficult because of these other contributions. Place the sample in a gelatin capsule with some cotton or a kimwipe piece to hold it in place. To prevent it from opening while purging, puncture a small hole in the top of the capsule with a needle or scalpel. The gel cap is then inserted into the center of a straw and held in place with 2 small pieces of a similar straw. The magnetization due to a uniform rod which is longer than the span of the pickup coils (such as the straw) will produce a constant flux, and does not contribute to the calculated magnetic moment. Stick the straw onto the end of the sample rod, making sure that the straw will not come off. Puncture another hole near the top of the straw to allow gas to enter easily into the region above the capsule. Then slide the quartz tube assembly over the straw. 

2) Before proceeding to load your sample into the MPMS, determine the instrument configuration. 

3) Cut the straw to the appropriate length (see template) and position the sample in the straw according to the template.

4)Prevent the sample from falling out of the straw by placing a small piece of Capton tape over the bottom of the straw. Then, make a hole in the tape with a paper clip to allow air to pass. Make small holes in the side of the drinking straw above the sample to allow air to pass. 


B) quartz rod
Another technique that can be used with tiny samples is to attach them to the side of a small quartz rod with a dot of vacuum grease. If this is done, centering rings should be attached to the top and bottom of the rod to ensure that the sample does not get scrapped off the rod as it is inserted into the sample chamber. 

If either of these techniques is used, the sample should be mounted about 7 to 10 cm from the end of the sample holder so that the end of the sample holder does not move through the detection coils during the measurement. The end of the sample holder will also produce a signal in the SQUID detector. If it approaches the coils closely enough to be detected, the signal will be distorted and the magnetic moment calculation for the sample will be in error. 


===== sample loading/removal =====


loading:

Once the sample is mounted on the sample rod, the following procedure describes the procedure for making a measurement: Installing the Sample Rod Assembly into the Sample Chamber 

1. Tighten the knurled nut on the slide seal assembly so that this portion of the sample rod is positioned approximately 122 cm (48 inches) away from the center of your sample. 

2. Pull the sample rod up through the slide seal so that the sample holder is drawn into the protective glass sleeve (the shroud). Make sure the top of the sample holder is flush against the bottom of the blue plug. 

3. Vent the sample chamber. a. If there is a sample present in the sample chamber, proceed to step 4. 
b. If there is no sample present in the sample chamber and the READY 
LED is on, vent the system by closing the airlock valve (this causes the sample chamber to vent automatically). Close the airlock by rotating the handle counter clockwise so that it points (horizontally) to the indicated CLOSED position. Wait for the VENTING LED to turn off. 
c. If there is no sample present in the sample chamber, the airlock is already in the CLOSED position, and the green READY LED is on; toggle the handle to OPEN then back to CLOSED. Wait for the VENTING LED to turn off. 

4. Open the slide seal clamps on the sample transport socket block so the blue plug or slide seal assembly may be released. 

5. Remove the blue plug or sample rod. If a sample is present, pull the sample rod assembly up until the sample is visible in the window. Make sure that you can see the bottom of the straw! 

6. Before proceeding, verify that the three o-rings in the blue plug socket block are in place, free of debris, and not dry. If necessary, apply a small amount of Apiezon M grease to the surface of the o-rings. 

7. Insert the sample rod into the sample chamber until the slide seal housing can be secured into the socket of the sample transport. Note: Ensure that the white “dot” (of the blue plug) is facing forward. This ensures proper gas flow through the slide seal. It may be secured by rotating the two rectangular handles on the socket block so that the slide seal is forced down against the three o-rings in the block by cam action. 

8. The blue plug of the slide seal assembly should be flush to the top of the socket block. 

9. Close the slide seal clamps on the sample transport so the slide seal assembly may be fastened. 

10. Press the button on the front of the MPMS probe labeled <PURGE AIRLOCK> to initiate automatic purging of the airlock. When the green LED labeled READY comes on, open the airlock valve by rotating the handle clockwise so that it points vertically to the indicated OPEN position. Note: If the READY LED does not light within a few seconds after the purging sequence ends, there may be a leak in the sample handling system or the annulus pressure gauge may be negative. Negative pressure is characteristic of acquiring low temperatures. The temperature must be stable before the READY LED will light. 

Watch the sample through the window to make sure it does not move or fall out of the straw. If the sample moves only a little (few mm), it is still OK; proceed to step 10. If it moves up or down too much, it will not be possible to center it. In this case, wait for the green <ready> light, open the sample chamber valve, then close it again, and return to step 3 to remove and reposition your sample. If the sample falls out of the straw, find a staff member for assistance. DO NOT ATTEMPT TO RETRIEVE IT YOURSELF! 

Purging the top chamber prevents air from being introduced into the sample tube. One wants especially to minimize the amount of oxygen contamination (which is paramagnetic), which can significantly contribute to the signal at low temperatures. Also, ice could accumulate and cause problems. If the sample tube does become contaminated (or if a sample falls to the bottom of the sample tube), it can be heated to ~320 K and purged with helium, i.e. with the airlock valve open. 

When the green <ready> light comes on*, open the sample chamber valve. If the ready light fails to show after a few minutes, there are two possible causes: 

a) The system is cooling to a set-point temperature. Check the current T and setpoint T. If the system is cooling, you can interrupt it: click on the temperature display, select Set Temperature, and enter a value near (slightly above) the current temperature. Once the new set-point is registered, the green light should come on immediately. You can then re-enter the original set-point T and continue with sample installation as the system cools. 

b) If the temperature is stable and the green light still fails to illuminate, there is probably a vacuum leak. 

11. Lower the sample slowly and slowly turn the rod during the insertion process. Note: If the rod appears to be dry or is not moving smoothly through the lip seals, place some Apiezon M grease above the blue plug. 

12. Lock the clip assembly into the actuator shoe by tightening the thumb nuts. 

13. Removing the Sample:

To remove the sample , first, loosen the two thumbscrews and rotate the black clip
assembly from under the thumbscrews. Slowly and carefully, pull the rod up while
rotating the rod. If there is resistance, or if you hear a squeaking noise, or the rod feels cold, STOP and pause 30 seconds while the O-ring and rod warm up. Pull the rod up
until you see the straw and quartz shroud in the airlock window. Stop when the Kapton
tape, where the top of the straw is mounted on, is at the top of the window.
Close the airlock valve, by turning the lever counter clock-wise until the lever is
horizontal. The airlock will automatically vent. Turn the cam levers off the blue slide
seal assembly. Pull the sample and rod completely above the sample transport,



===== sample centering =====


For best results, make sure the temperature is stable before centering. 

1a) Turn Autosample Tracking on. If it is already on, toggle it off then on again to ensure it is recognized by the MPMS software. 

1b) Initialize Sample Transport in order to calibrate the transport to 0.27 cm from the bottom limit of the transport movement range. This position is high enough above the transport limit to allow for movement to correct for thermal contraction in the sample rod when the temperature is lowered. 

2) Click on the Center menu on the top of the screen. 

3) Select DC. 

4) Run the Center procedure. A SQUID response curve will be displayed in about 30 seconds. The response curve should be symmetric with the large central bump (up for positive fields or moments) centered on the plot, as in the example. Check the magnetic moment; if > 0.5 emu, remove your sample, decrease the amount of material and re-start. If there is not a recognizable central peak (positive or negative), there are two things to try: 

a) Apply a small field (e.g., 10 G or 100 G; click on the field display panel on the bottom of the screen and enter the desired value). For weak samples that have not been previously magnetized, this may help to generate a measurable signal; 

b) Try a Full DC Scan. If the sample is far from the correct location, this full-length scan is a more effective way to detect its position. 

5) Click on Adjust Position to verify that the Sample Location is at the middle of your scan (2.00 cm for 4-cm scans). If it is not, run the Adjust Automatically procedure. 

6) If the sample is too far off-center, you will not be able to adjust the position automatically. Adjust Manually procedure, which involves loosening and tightening the knurled nut on the sample rod, as instructed by the software. 

7) Rerun the Center procedure to make sure your sample is really centered. 

If centering does not work properly go the the menu “Measure”, to “DC”, choose algorithm “iterative regression”. Try again centering 



===== software setup and running experiments =====


The panel on the left side of the screen contains controls for specifying data files for output or for graphing, and for selecting and running sequences (experiments). 

1) The top box indicates the sample name. You can click on the Change button below to change the sample name, mass, etc. for the header of the data file. You can also click on the Install/ Remove button to remove your sample and insert a new one. 

2) The second box show the currently selected Sequence File. Experiments are run by executing Sequence Files, which contain all the necessary instructions for temperature and field control, data acquisition, etc. To view the contents of the current sequence file, click on the Edit button. An edit window will open, and will display the contents of the selected file. To close the edit window, click on File and then Close. To view a list of sequence files, click on the Change button below the sequence file name. You can scroll through the list displayed, and select a file by double-clicking on its name. If you wish to modify any of the existing files, consult a staff member. 

3) The third box on the left panel is labeled Sequence Base Data File Name. All data collected by the sequence as it executes will be stored in the file designated in this box. To specify a new file, click on the Change button below the sequence file name. You can use the control buttons to change directories, or to create a new directory for your files. 

4) When you have decided which sequence you wish to run, and have specified an output file, you can begin the experiment. The fourth and final box on the left-side panel is the Sequence Control box. Click on the Run button to begin the experiment. 

5) To generate a graph of the data as the measurements are being made, click on the View button below the Sequence Base Data File Name box. A list of relevant files will appear, generally including a lastscan file, which allows you to look at the SQUID response curve for the previous measurement, and a dat file, containing magnetic moment as a function of temperature, field, etc. (The file list will be empty until the sequence actually begins collecting data). 

Here are some suggestions for setting the experimental parameters: MPMS EXECUTIVE MENU: 1. Use magnetic mode OSCILLATE unless you are measuring hysteretic samples. The field is more stable in time when you oscillate to the final value. Also, the remnant field (due to trapped flux in this hard, Type II superconductor) will be smaller. 

2. Use temperature mode UNDERCOOL ON for faster cooling, unless you are concerned about hysteretic effects. 

3. MAG HIGH-RESOLUTION (ENABLE) COLLECT DATA MENU: 
1. Use iterative regression mode algorithm for determining the moment. 
2. Use 3 cm scan length. 
3. Take 32 data points per scan & record 32 readings per point. 
4. Average 3 scans. 
5. Longitudinal autorange ON. 
6. If there is plenty of printer paper, Hardcopy ON & Plot after final scan. 
7. Make sure you change the filename. 


h. Start the run Although the second derivative coil arrangement will cancel constant H and dH/dx, it is very sensitive to external magnetic fields which change in time. Therefore, while a measurement is being made, activity near the QD MPMS should be minimized. You especially do not want to be moving large magnetic objects like LHe storage dewars or gas cylinders. Be aware that external RF sources can also produce noise in the system. Although we do not have one for the MPMS, a magnetic shield would greatly reduce these types of problems. 

i. After the run is finished: Set instrument standby and H = 0 to conserve helium and as a courtesy to the next user. Loosen the knurled steel nut on the sample rod and pull the rod up slowly. When you feel resistance, do not force the rod up - wait just a few seconds for the slide seal to warm up, then you can pull up some more. When the rod is all the way up, you can see your sample in the airlock. CLOSE THE AIRLOCK VALVE, then remove the sample rod. Replace the blue plug. 

j. Retrieve your data: copy the data file with the *.DAT extension to a floppy disk. This produces data in a column format that you can then analyze with any spreadsheet program. 


AC measurements manual
(revised by Tibi Sorop) 

Before doing any AC measurements please read careful the text listed below 

sample centering AC

1) For best results, make sure the temperature is stable before centering. Choose the temperature as close as possible to the starting point of your measurements. Do not do, for instance, the centering at 300 K and then start measurements at 4 K. 

2) Apply a certain value of field in the magnet. 

3) Click on the Center menu on the top of the screen. 

4) Select first DC centering 
Select Initialize transport 
Select Parameters: 6 cm (it is crucial to have 6 cm and not other value) 
enable autoranging 
enable autotracking 


5) Perform first a full range DC scan. Detect on the basis of this scan and on the indication on the table next to the SQUID where is the sample situated. 

6) After you have detected the position of the sample select Adjust sample position automatically command. Check if the dipole-signal is displayed in the figure. In case it is not repeat the previous command. In case you have obtained a good signal go to the next step. 

7) Perform AC centering. Please note that this is usually optional. It should be possible to make good AC measurements even without performing AC centering scan. However, in case you wanna be sure that everything will go as planned you can do also AC centering. 

8) Choose AC centering from the Center menu at the top of the screen. Do not initialize transport after the DC centering has been performed Select Parameters: define amplitude 
define frequency 
use autoranging 
specify number of datablocks the program averages for one measurement (1-264) 
verify that autotracking is on 
disable drive nulling 
define the length in time (sec) of the SQUID settling time, 
Select Center 


If the sample is not centered properly, then Adjust position (AC centering box). Please note that for performing AC centering one doesn’t usually need to apply any DC field (there are some cases however when the signal for DC field 0 is very small; in those cases, of course, one should apply an external field) 

9) If centering is not successful go to (11). In case the centering is performed successfully then first test the measurement before starting a long sequence and then realize after half a day that the measurement was useless. In order to test you can do a manual measurement as follows: 
Select Measure > AC 
Select Parameters: select coordinate system (amplitude/phase or system) 
define amplitude of AC drive signal 
define frequency 
use autoranging 
define amplitude of the waveform the system uses to null the AC drive signal 
specify number of datablocks the program averages for one measurement (1-264) 
specify the number of individual 2 point measurement the program averages 
verify that autotracking is on 
define the length in time (sec) of the SQUID settling time, 
include diagnostic data 
Select Measure 


10) Finally write your sequence and pray that it will work; 

11) The following steps should only be followed if AC centering is not successful. First try again AC centering procedure (7-10). If it still doesn’t work then consider resetting the Quantum Design MPMS controller (situated in the middle position of the rack next to PC). Please follow carefully the steps described below: - First set the magnetic field to 0 - Close the MultiVu program in a safe way - Go to the rack and press the power button in order to switch OFF the MPMS Controller (Model 1822) - Wait few seconds (recommended 1 minute) - Press again the power button in order to switch ON the Controller - Go back to the PC and double-click on the MPMS MultiVu icon to re-start the program (please pay attention and do not double click on the MPMS MultiVu Simulation Mode icon). - Print screen and record any error that is eventually displayed at this stage on the screen. - If no major error is displayed then continue with the program. The first thing you should do is to set the temperature to the value that it was before. Even if the temperature is shown on display to be the desired one you should still set it manually (when the MultiVu is initiated the temperature is not properly controlled and it shifts continuously). - Go directly to AC centering and try it again. - In case it still doesn’t work then follow the same procedure as described above (switch OFF the program;) but this time before switching OFF the MPMS Controller reboot the PC. - If it still doesn’t work then call Ruud 




===== Fishing lesson Or How to recover a sample =====

that has been dropped inside the Sample Chamber (by Tibi Sorop, dec 2005) 
If a sample falls off the sample holder or the sample chamber becomes contaminated, the MPMS is designed to allow the sample chamber to be opened to room temperature without danger of plugging small gas tubes or otherwise degrading the operation of the system. Simply set the system temperature to room temperature or slightly higher (about 310 Kelvin); when the system becomes stable at that temperature, the airlock can be opened to the room. 

Be prepared with a long stick (check in the cupboard) and with double sided tape. 

1) Remove the rod and close the Airlock Valve 

2) Set the temperature to 300-310 K and keep it for a while (15-30 minutes) 

3) Go to Utilities/Diagnostics/Chamber (before you start operating changes at the status of the valves you should keep in mind that during the normal operation i.e. during measurements the valves are like follows: FLUSH VALVE: open/ VENT VALVE: closed) 

4) Press open VENT VALVE: (only) the airlock will be vented (don’t forget to press SET command every time you modify the status of a valve, otherwise the change will not take place). 

5) Open the Airlock Valve 

6) Press close FLUSH VALVE 

7) Press open VENT VALVE in order to vent the sample chamber 

8) Try to remove the Airlock Plug; if everything is done correctly it should be easily removable. If not it means that probably the system is under vacuum and therefore you should check the previous steps 

9) Take the stick with the double sided tape and start fishing carefully; try to remove all the parts of the sample in case you suspect it might be broken in pieces. 

10) When the sample was found and removed you need to reset the system to the normal operation mode by doing the opposite steps 

11) Close the Airlock Plug 

12) Press close VENT VALVE 

13) Press open FLUSH VALVE 

14) Close the Airlock Valve 

15) Press close FLUSH VALVE 

16) Open Airlock Valve and then close it again to check if the Green Light functions again properly 

17) You can now continue with the normal operation of the system 

18) In case that any of the above operations goes wrong inform Ruud Hendrikx immediately. 
MPMS-xl: after not using for some time the rotary pump might not work. Remove power cable, remove covers,
rotate axis by hand until it runs smoothly. Reinstall everything, reconnect power cable. The pump should 
run now.




===== Troubleshooting =====


Because the pump pumps relatively large volumes of Helium, the rotary pumps loose oil to the exhaust. Once every few weeks, check the oil level in the drain and remove the oil.

For serious problems: contact  Stefan Riesner/ Thamas Beppler at Lot-Oriel, Darmstadt, Germany. \\
Stefan Riesner \\
Phone +49 6151 880667 \\
E-mail: riesner@lot-oriel.de \\


Thomas Beppler \\
Phone +49 6151 8806573 \\
E-mail: beppler@lot-oriel.de \\



===== Calibration/Configuration files =====

* MPMS_5s \\
 {{data:calibr_5s.zip}}

* Squid Ac en Dc calibration \\
{{:data:squid_ac_dc_calibration.doc|}}

* Calibration of ac and dc magnetometers with a Dy2O3 standard \\
{{:data:chen2011revsciinstr_dy2o3_ac.pdf|}}

===== Quantum Design service notes =====

* ** Connector test** \\
general test \\
{{:equiment:squid:mpms_black_lemo.pdf|}} \\
{{:equiment:squid:mpms_probe_resistances_all.pdf|}}

* **Flow test** \\
check if cooling heating isn't fast (10K/min) \\
{{:equiment:squid:high-power-impedance-test.mv.pdf|}}

* **Model 1802 heater/valve driver output** \\
check if cooling heating isn't fast (10K/min) \\
{{:equiment:squid:1014-307_output_drivers_m1802_multivu.pdf|}}

* **Model 1802 fuses** \\
check if cooling heating isn't fast (10K/min) \\
{{:equiment:squid:1802-which_board_is_where_1.jpg‎?width=120px}}
{{:equiment:squid:m1802_rare_panel_fuses.jpg?width=120px}}
{{:equiment:squid:power_board_fuses.jpg?width=120px}}
{{:equiment:squid:voltages-1802-power-supply.jpg?width=120px}}
{{:equiment:squid:voltages-1802-zoom.jpg?width=120px}}

* **Kepco Powersupply Tests** \\
With the following procedutre one can test the kepco PS independantly from the MPMS electronics this way we find out if the is at the electronics or at the Kepco:

Attached bench test should help to coarsely evaluate the Kepco's ability to deliver current. Disconnect the wires from MPMS Gas/Magnet Tray to Kepco rare panel, 
connect an external power supply and wires electrically as shown in the schematic. Ramping the external power supply from 0 to 5 volts should cause adequate 
output of the Kepco voltmeter and 0-50 ampers output of the current.

Make sure the shunt will be at least 0.1 Ohm - otherwise the test will fail and the Kepco will rail through to max current output, immediately.

---------------

The following info is Only for experienced users who has no possibility to send it back.

We usually see Kepco failures with the big 70 Amp, rectifying diodes, big capacitors or the 12 2N3055 transistors.
Your MPMS hardware manual binder should contain complete Kepco manuals that hold functional description, testing procedures, schematics and part lists for repair reference.

{{:equiment:squid:kepco_test_circuit_1.jpg?width=120px}} {{:equiment:squid:kepco_test_circuit_2.jpg?width=120px}} {{:equiment:squid:kepco_bench_test_circuit_setup-1.pdf|}}