1. Procedures for changing the Turret on the TIMS

 

Loading Pb on Re filament.

 

Sonicate Si gel 20 min.

Add sample first, 2ul or less each time till sufficient amount is reached

(* If loading standard aim for 100ng which is 2ul if the concentration is 50ppm).

Dry down samples at 1amp.

Add 2ul si gel and 0.4ul 0.5 M H3PO4.

Dry at 1.3 amps completely,

Turn the current up to 1.5 to remelt the sample, wait till the sample turns white on the filament, then turn up the filament slowly to 2.4.

Finally the sample on the filament should be smooth and white.

Conny's tip, always add in by 1-2ul sample.

 

For double spike, put a drop of double spike on parafilm, mix 25ng sample with 25ng spike (1:1).

 

Load Sr on W filaments

 

Load 2ul of sample first @<1.2 Amps,

Then add 2ul Sr loader @ 2.0 Amps,

Turn up the filament to a faint glow (@ ~2.   Amps) to burn off Rb

(***If in the end the sample solidifies into a solid white paste, especially when it cracks, that means the loader is too concentrated. You should dilute the loader.)

 

Load Nd on Re filaments with Si gel

 

Sonicate Si gel for 20 minutes.

Load 2-4ul Si gel.

Dry down sample @ 1.7Amp till it becomes a thin wet film.

Turn down the current to 1.0 amp and dry down the remaining Si gel.

Add sample onto the Si gel spot then let it dry @1.2amps.

Sample bubbles.

Then turn up till faint glow for 1 sec (with ambient light off).

 

Load Nd on Re filaments without Si gel

 

Melt parafilm on both ends of the filment (@ 1.5 Amp)

Load 50-100 ng Nd sample

Dry it down at 1.2 Amps

?? Add anything???

Turn up the filament current to ~2 and wait till the parafilm evaporate.

 

Loading the Turret:

 

1) Always wear clean gloves when operating inside the source housing.

2) Always have enough empty space on the table and have some clean white paper on the table to set the source wipers and the turret on.

3) Insert the metal blocks into the turret and tighten the bolts if needed.

4) Take your sample box and the sheet of paper with loading information and fill the turret according to the order that you loaded. Note, the block numbers on the turret are written on the right hand side of the screw. Also note that the block positions are not continuous. Rather, each number is off from its neighboring number by 3 (e.g., 1 next to 4, etc.). Therefore it is recommended that you pay attention to the sequence that you load your filaments onto the turret to avoid any confusion.

5) Secure the posts on the blocks with the screws and make sure that the flat side of the posts face outwards from the center.

6) Place clean cover slips on each block. Often times, to make sure the cover slips clamp onto the blocks, it is necessary to first hold the two sides of the cover slips and bend it towards each other a little bit. For blocks that are closed on the end use the cover slips that are open ended. For blocks that are open on the end you can use either the open or closed ended cover slips.

7) After installing all the cover slips, turn the turret around and look through the slit openings to make sure that the slit openings are reasonably aligned with the filaments.

8) Pick up the turret and shake it a bit to check if there are any loose cover slips. Also double-check if any cover slips have pointy edges on the flat side of the turret, if so, flatten it so that it wouldn’t scratch the inside of the source housing.

 

Changing the turret:

 

1) Be sure the Mass spec is ready: i) LOS valve closed; ii) high voltage off; iii) filament current off; iv) the ion gauge is switched to off position.

2) Close the backing pump (roughing pump) valve first (the black knob under the source housing), then turn off the turbo pump (press the on/off switch next to the green indication lights on the control panel under the flight tube)

3) Wait till the airflow through the desiccator tube slows down before opening the source housing. Even though it is very easy to break the vacuum by forcing the cold finger on top of the source housing open, it is not recommendable at first, as moisture will rush into the source housing making it harder to be pumped down later.

4) Remove the wiper plate unit after loosening the 2 screws. Place it on a piece of clean paper with the wipers facing down and the delicate wires facing up as the wires are easily bent which could cause shorts in the source later.

5) Remove the turret currently inside by attaching the turret tool and turning only the gray plastic knob of the tool counterclockwise while holding the metal part of the tool still.

6) Place the turret flat side down on a piece of clean paper and cover it with plastic wrap.  Often time people like to save some filaments for the near future. In this case you should mark the name of the person on the paper and notify him/her through email so that they can properly store their filaments. Any filaments left unclaimed will be reused soon.

7) Insert the new turret in the source housing with the help of the turret tool, then detach the tool from the turret by turning the knob clockwise. 

8) Replace the wiper plate and tighten the two screws. Try to insert the wipers between two blocks with no filament posts caught in between the wipers. DO NOT force the wiper plate in while replacing it. It often gets stuck because the filament posts are stuck in between the wipers, which can be mended by turning the turret a little bit. Forcing the wiper plate on might damage both the wipers and the filament posts.

9) Standing on a stool and looking down from the cold finger window. Carefully rotate the turret to check if EVERY filament posts are correctly aligned so that they can go in between the 2 middle wipers in BOTH directions. The wipers should only be deflected slightly. Otherwise the filaments might be damaged during automatic runs. A perforated block tool is available to align the filament posts.

10) Before closing the door of the source housing, wipe the perimeter of the door with Kimwipe and methanol. Wipe the o-ring with QD water and dry Kimwipe. Any lint or dirt on the sealing area will lead to poor vacuum, which might require re-opening of the source housing later. Close the door of the source housing, push the right hand side of the door all the way in so that the door is properly closed and sealed all around.

11) Replace the cold finger. Also wipe the perimeter of the contact area with a Kimwipe and some methanol. Wipe the o-ring with QD water and dry Kimwipe. Double-check that the O-ring is well seated before you replace the cold finger.

12) With all these done you are ready to put the source under vacuum again.  Turn on the

Turbo pump switch first, then go to the back of the machine and close the amplifier-housing valve. Afterwards re-open the black roughing pump valve under the source housing. Wait till the pressure on the pirani gauge drops to 10^-2 before re-opening the amplifier housing valve at the back of the machine.

13) Wait ~15 minutes, then turn on the ion gauge (with source filament). Observe the reading and check if the pressure reading slowly decreases. If not, then you may have a leak somewhere and you should start from checking the seals of the cold finger and the source housing.  

 

2. Running the TIMS

 

Policy on using Liquid Nitrogen:

 

LiqN2 should NOT be used to reduce pump down time.  Anyone who uses it in this manner is liable to lose laboratory privileges.

If LN2 is used, the reservoir must be monitored and re-filled.  Do not allowed it to run out over the course of an isotope analyses.

 

TIMS Logbook:

 

It is essential that everyone keep a record of analyses in the Logbook, even if you want to type in your results later and attach a neat print out, certain information must be logged in by hand.

 

At the beginning of each day, each user must log in:

1) Name

2) Date.

3) Types of analyses to be run (e.g. Sr isotopes).

4) Types of samples to be run.

5) Temperature and humidity.

6) Source pressure High voltage for a good mass calibration.

7) Flight tube/analyzer pressure read from the ion pump gauge under the flight tube.

8) After finding a signal, one should also log in the final HT setting.

 

The record of the results must be logged in within a day of running. Nobody likes to yell at others, so if someone has to yell at you for not logging in your data, apologize and do it right away.

 

Comments are useful for all users.  Comments on the behavior of the instrument, etc. should be written in the log book whenever possible. If anything strange is observed, it should be logged.

 

Rebooting the machine:

 

Sometimes when the computer is left idle for a long time, or if you suspect that a miscommunication exist between the Mass spec and the computer, then a reboot might help.

 

Sometimes when the computer is left idle for a long time, or if you suspect that a miscommunication exist between the Mass spec and the computer, then a reboot should be attempted.

 

1) From the computer, “Esc” to DOS and then turn off the power.

2) Go to the control panel, in the exact sequence, turn off the Filament supply, HT, magnet supply, and on the left panel from top to bottom turn off the three control for the acquisition units (see figure 2e of the bakeout manual).

3) Wait for one minute.

4) Turn on the three controls for the collector units on the right panel first from bottom up, then switch on the magnet supply, HT, filament supply.

5) Wait till the large panel of the collector units reads “Free run”, switch on the power for the computer.

6) After the computer enters the main page, choose the account that you usually log into. When prompted with the Y/N question for returning to the last operational setting, enter N for No. Note that the faraday motor drive is not connected, other than that there shouldn’t be any other error message normally.

 

Turning up the high voltage (HT):

 

1) Switch the HT to on from the control panel.

2) Turn the high voltage to 4000 v from the computer (F7 à 4000).

3) Watch the HV gauge on the instrument rack for at least 15 seconds.  The needle is often stuck, so either enter an even higher number to give it more force or tap the dial lightly to loosen the needle. However, once the needle is loosened, if it becomes unstable, turn down immediately.

4) Turn the high voltage to 6000 v.

5) Watch the HV gauge on the instrument rack for at least 15 seconds.  If the needle is unstable, turn down immediately.

6) Check the last HT reading.

7) Turn the high voltage to the last HT reading.

8) Watch the HV gauge on the instrument rack for at least 15 seconds.  If the needle is unstable, turn down immediately.

 

Running Sr

 

Make sure to run a few reproducible NBS 987 standards before running the real sample. The ideal 2SD reproducibility for NBS 987 is less than 30 ppm or +/- 0.000021. The accepted value for NBS 987 is 0.71024. All measured values should be corrected relative to the accepted standard value by taking into account of the difference between your measured average standard value and the accepted value.

 

Throughout the heat up period, keep an eye on the pressure (source filament on the ion gauge).  If the pressure goes up suddenly, stop what you are doing or even go back a few steps until the pressure goes back down before increasing the current further.

 

1) Turn up side filament current coarsely to ~1.2 amps. (F6 à up)

2) Continue more slowly, watching the source pressure for sudden pressure increase. Heat up the filament till a faint glow (usually ~2 amps).  If the source pressure increases, stop, decrease filament current one step, and wait a few moments for the pressure to stabilize.

3) Make sure mass is 88 (F4 à 88)

4) Open LOS and check to see if there is a signal on mass 88 at this point.  (L opens and closes the LOS)

5) If there is no signal on mass 88, keep turning the filament up in fine steps until you see a signal.

6) Continue with the Sample or Standard, depending on what you are running.

 

Standards:

1) Open the LOS and increase filament in fine steps to a few hundred mV of 88. (L controls opening and closing of the LOS, F6 à up increase current)

2) Autofocus  (F5 à A)

3) Turn the filament up until the 88 signal is ~1 Volt (F6 à up)

4) Peak center, then fine-tune the HT till the mass center falls between 87.99 and 88.01 (F 7 à P)

5) Turn filament up until signal is ~2 Volts

6) Autofocus

7) Peak Center, then fine-tune the high voltage

8) Turn up side filament until signal is ~4 Volts

9) Autofocus

10) Peak center

11) Run srdy88ax experiment (Escape the control window, F5 à Procedures à Analyses à srdy88ax with the command highlighted as “modify” and check the parameters before proceeding to “run”).

12) Write down the file name, intensity, Rb, 86/88 ratio, 87/88 ratio, accepted/measured ratios, and error into the logbook. Double check the cup alignment by comparing the stable isotope ratios measured on 1-2 vs. 2-3 cups. They should be very similar. Also 86/88 ratios lower than 0.19 indicate over fractionation, in which case the final value is not reliable.

 

Samples:  If your sample has Rb, then it should be burned off.

1) Change the mass to 85 or monitor all ten cups

2) If there is a signal (higher than other baselines) on low 3 with 88 on the axial, close the LOS, note starting filament current, and turn side filament up quickly in coarse steps to 3.3 amps (temperature?), hold for a short moment and quickly turn it down to previous level.

3) Wait for 1 minute then open the LOS valve and make sure there is no longer a signal on mass 85, repeat step 2) if necessary

4) Change the mass to 88.

5) Continue as with a standard

 

Running Rb ID

 

?? Spike

 

 

Running Pb

 

Make sure to run a few reproducible NBS 981 standards (both unspiked and double-spiked) before running the real sample. The ideal 2SD reproducibility for the standard is less than 300 ppm for 206/204, 207/204 and 208/204. The accepted value for NBS 981 is from (206Pb/204Pb 16.9356, 206Pb/204Pb 15.4891, 206Pb/204Pb 36.7006) (Todt et. al., 1996). All measured values should be corrected relative to the accepted standard value by taking into account of the difference between your measured average standard value and the accepted value.

 

Throughout the heat up period, keep an eye on the pressure (source filament on the ion gauge).  If the pressure goes up suddenly, stop what you are doing or even go back a few steps until the pressure goes back down before increasing the current further.

 

1) Make sure you use the latest Pb program.

2) Run standards first.  This way you will get a feel for running and comfortable with signal intensity.

3) Raise filament current with coarse adjustment until filament reaches ~ 1000-1050º. It is very important to use a pyrometer.

4) Use fine adjustment to raise filament temperature to ~1100º. If 50 ng was loaded there should be a pretty large signal.  IMPORTANT NOTE – Watch the pressure in the source with each increase in the filament current.  If the pressure goes up past 1 x 10^-6, wait until the pressure drops before raising temperature further.

5) At 1100º open the LOS – you should see a beam on Pb

6) Focus the beam several times

7) Do a peak center

8) Increase the intensity until you have at least 3.7 V on 208Pb or 100 mV on 204Pb stopping to peak center, focus, and just generally take it easy on the way up to this intensity.

Monitor the temperature of the filament constantly and record this in your notebook

9) When you’ve reached at least 1200º and you’re satisfied that everything is focused and centered, run the sample.

10) Make sure blocks plot on Pb fractionation lines.

11) Ha! You thought you could rejoice and do a dance?  No such luck.  You must do both double spiked and unspiked analyses to get data.

 

Running Pb concentration

 

Add 205Pb spike to the samples before chemistry.

Make sure to align the 205Pb cup with the rest.

Run …. program

 

 

Running Pb blank

 

Load the dissolved blank onto the filament (one blank on one filament)

Make sure the necessary cups are aligned.

During running, bear in mind that there is limited amount of Pb on the filament, therefore you need to be fast and precise.

Turn up the filament coarsely to 1.2 Amps.

Then turn up finely to the normal running temperature (1100 degree C)

Open the LOS, you should see a small signal on the spike that you loaded, be it 206 or 208. Auto focus till you find a beam then increase the temperature to 1200 degrees. 

If the signal on 208 is 1 volt, run the normal Pb program. 20 ratios should give a decent average.

Plug into the spreadsheet to calculate the blank.

 

Running Nd

 

Make sure to run a few reproducible standards before running the real sample. The established international standards in the lab are La Jolla and Jndi-1. The ideal 2SD reproducibility for 143/144Nd is less than 50 ppm. The accepted value for La Jolla is 0.511858 +/-7 (Lugmair and Carlson 1978) and Jndi-1 is 0.512115 +/-7 (Tanaka et. al., Chemical Geology 2000). All measured values should be corrected relative to the accepted standard value by taking into account of the difference between your measured average standard value and the accepted value.

 

Throughout the heat up period, keep an eye on the pressure (source filament on the ion gauge).  If the pressure goes up suddenly, stop what you are doing or even go back a few steps until the pressure goes back down before increasing the current further.

 

1) If you are the first person to measure Nd after a turret change, with the HT and filament current OFF, allow O2 to leak into source chamber until the pressure reading is ~4.5 x 10^-4 mbar.  Hold for ~20 seconds, and close the oxygen.

2) Set mass to 160 and turn up the HT (See previous section for details on HT).

3) Turn up filament current coarsely to ~1.2 amps.  (F6 à up)

4) Continue more slowly, watching the source pressure to make sure the filament does not outgas, to a faint glow (usually ~2 amps).  If the source pressure increases, stop, decrease filament current one step, and wait a few moments for the pressure to stabilize.

5) Allow Nd filament to stew at the faint glow for 30 minutes.

6) Open the LOS and increase current on filament in fine steps until you see a signal.

7) Autofocus.

8) Increase filament in fine steps to some tens of mV of 160.

9) Peak center and set HT so that the center is between 159.99 and 160.01.

10) Slowly open O2 leak valve until the source is at a bit lower than 1 x10^-6 mbar.  Do not exceed this pressure.  The signal intensity should at least double.

11) Autofocus.

12) Turn filament up until signal is at least 500 mV.

13) Sample is ready to run.

14) During the run, write down the file name, intensity, Pr, Sm content, 146/144 and 145/144 ratios and the final corrected 143/144Nd isotope ratio, number of ratios accepted/measured, error info into the log book. Double check the cup alignment by comparing the 146/144 or the other stable isotope ratio measured on sequence 1-2 and 2-3. The two ratios should be very similar. Also, mass fractionation can be monitored with the two stable isotope ratios. 146/144 increases as fractionation proceed, values higher than indicate over fractionation.

 

Running Sm ID

 

Load Lames spike