Date: Wed, 21 Aug 2024 17:12:41 +0200
Hi Jennifer,
This is the piece of wire I am using. It is taken rom 16 mm²
cross-section electrical wiring, and the long leg is about 30 cm long.
In retrospect, I would probably have made it slightly longer to reach
all the ice for sure, but until now I have not had problems anymore
after removing everything I could reach with the piece on the picture.
Cheers,
Matthias
On 17/08/2024 21:51, Jennifer wrote:
> Hi Matthias,
>
> May I ask a picture of copper wire you are using for de-icing?
>
> Jennifer
>
>
>> On Aug 17, 2024, at 11:28 AM, Josh Kurutz via groups.io
>> <jkurutz=uchicago.edu_at_groups.io> wrote:
>>
>>
>>
>> Hi Wendy et al.
>>
>> How’s the weather? Literally, has your area been experiencing rapid
>> changes in barometric pressure?
>>
>> Years ago, I had an Oxford 600 with a lineshape instability problem.
>> It would degrade over time, but the rate of decay wasn’t consistent,
>> and sometimes the linewidth would actually recover (getting sharper
>> with time after having gotten bad). I ran a long-term experiment
>> acquiring a scan every half hour (I think), plotted the linewidth
>> over time, which demonstrated it was changing at varying rates. I
>> found that plotting linewidth as a function of atmospheric pressure,
>> as recorded at the nearest airport,* showed a very strong dependence.
>> We installed a manostat to stabilize the helium pressure in the
>> magnet, and that mostly cleared up the problem.
>>
>> I’ve encountered other lineshape stability problems on various
>> instruments, including some pretty bad problems with a new magnet
>> (which has since mostly stabilized). I’ve got a pretty standard
>> approach for gathering data now, developed in part with Bruker service:
>>
>> * Shim a lineshape standard as sharp as practical
>> * Run a kinetics experiment for a desired period (4 hours to
>> weekend, depending on need and other factors)
>> o Pulse program kx_zg2d, Bruker parameter set KX_PROTON_2D
>> o One 1H experiment with lineshape acceptance test parameters
>> every 15 or 30 minutes
>> o Keep locked or unlocked, depending on whether you think
>> there’s significant coupling of a shim to Z0, like if your B0
>> field was also drifting strongly
>> o Keep Autoshim on, selecting suspected problem shims (for me,
>> usually Z, Z2, Z3, X, Y, XZ, YZ), interval = 3 sec, delta = 1
>> unit for each
>> * While the kinetics experiment is running, also run a script that
>> tracks your shim values (writes them to a text file at specified
>> intervals, like every 10 or 15 minutes, depending on how fast you
>> see your lineshape degrade). Earlier in this thread (Aug 12 for
>> me), Mike Groves mentioned such a script. I think he tried
>> attaching it, but my system gave me warning message that said an
>> attachment was removed. While troubleshooting a new magnet, Bruker
>> Service sent me a script called “followshims” that performs this
>> function, and works OK. I don’t feel right passing along their
>> script, but I suggest you reach out to them for a copy.
>> * Analysis: After determining whether the Autoshim routine
>> faithfully kept the lineshape on track, plot the values for each
>> shim against time, and see if any were drifting. With this data,
>> you can identify which shims are more problematic and perhaps try
>> correlating changes with possible causes, especially those that
>> can be associated with time, like atmospheric pressure, room
>> temperature, elevator traffic, etc.
>> o I imagine if you’re having a problem with a specific cryoshim,
>> it will show up as a strong change in the corresponding RT shim.
>>
>> For extra certainty with respect to the environment, I suggest getting
>> a temperature/humidity/pressure logger (which is already a good idea
>> for tracking HVAC problems). Placed near the magnet, you can plot shim
>> values as a function of these parameters with whatever frequency you
>> choose, like every 15 minutes. This is the kind I use:
>> https://lascarelectronics.com/data-loggers/pressure/el-sie-6-plus/
>> <https://lascarelectronics.com/data-loggers/pressure/el-sie-6-plus/>
>>
>> I hope this helps. Good luck!
>>
>> * Josh
>>
>> * For records of recent weather observations in the U.S., see
>> https://www.ncei.noaa.gov/access/search/data-search/global-hourly?pageNum=1
>>
>> Josh Kurutz, PhD
>>
>> NMR Facility Manager, Chemistry Dept.
>>
>> University of Chicago
>>
>> https://chemnmrlab.uchicago.edu/ <https://chemnmrlab.uchicago.edu/>
>>
>> jkurutz_at_uchicago.edu
>>
>> *From: *main_at_ammrl.groups.io <main_at_ammrl.groups.io> on behalf of
>> Matthias Brandl <matthias.brandl_at_tum.de>
>> *Date: *Friday, August 16, 2024 at 3:34 AM
>> *To: *main_at_ammrl.groups.io <main_at_ammrl.groups.io>
>> *Subject: *Re: [AMMRL] Off axis shims bad after 24 hours on
>> 40-year-old Oxford magnet #Bruker #Hardware
>>
>> Hi Wendy,
>>
>> We have had partial and full nitrogen port blockages several times
>> even with heat exchangers installed on the turrets, probably due to
>> some combination of bad seals and suboptimal filling practices.
>>
>> While I have not heard any complaints about bad lineshapes from that
>> (though that might not mean much), I have used a piece of large-gauge
>> copper building wire (the kind that contains a small number of
>> relatively large individual strands) to check for a blockage and, if
>> one is there, remove it. I have cut a piece of that about 30-40 cm
>> long, stripped it and put a dogleg in one end to avoid dropping the
>> whole thing into the nitrogen tank, and also keep the strands together
>> a bit better.
>>
>> I use this to rasp the ice away (rotate at first, then at some point
>> scrape the walls of the tube). The copper should be sufficiently soft
>> to not hurt anything, at least that is my hope.
>>
>> Cheers
>>
>> Matthias
>>
>> On 16 Aug 2024 01:13, John Decatur <jdd13_at_columbia.edu> wrote:
>>
>> Hi Wendy,
>>
>> Many years ago my 500 spectrospin magnet (now 40 years old
>> coincidently) would suddenly go to a terrible line shape (and this
>> was before Topshim so it was very painful to shim it back.) Turns
>> out the source was a nitrogen port that was getting partially or
>> fully blocked and this caused the magnet/dewar to shift and the
>> homogeneity to change. I didn’t have the metal heat exchanger fins
>> on the exhaust ports but only tubing over the port. The seal
>> between tubing and port was not perfect so when we did helium
>> fills, air would sometimes get sucked back into the LN2 can,
>> blocking the port. Replacing the tubing with metal fins solved
>> the problem and the magnet has been stable ever since.
>>
>> Another possibility (remote likely) could be changes in the RT
>> shims during VT experiments. Do you do VT often? I find my shims
>> get hot or cold during VT which causes homogeneity shifts and then
>> they drift back to RT slowly and that is with a large amount of
>> air purge down the bore.
>>
>> And of course, make sure that RT shim stack is tight as others
>> have suggested! To me it doesn’t sound like a potential quench
>> but something is moving or perhaps as Charlie has suggested, an
>> unstable power supply or bad contacts.
>>
>> john
>>
>> On Aug 15, 2024, at 5:32 PM, Karel Klika <karkli_at_utu.fi
>> <mailto:karkli_at_utu.fi>> wrote:
>>
>> Hi Wendy,
>>
>> Your problem reminds me of a problem we had many, many years
>> ago. We had an NMR for which the shims would suddenly go bad,
>> as in 20% spinning sidebands. This would happen intermittently
>> and seemingly out of the blue for no apparent reason.
>> Readjusting the shims (even by the instrument manufacturer
>> engineers since the instrument was still under warranty) would
>> resolve the problem for a period of time but sooner or later
>> the jump to bad shims would happen. Looked at every possible
>> cause you could imagine... But one day when I was tuning and
>> matching the probe by physically getting down on the floor and
>> adjusting the tuning knobs I noticed the shim stack could
>> move. Turns out the problem was simply a loose holding screw,
>> tightened it, adjusted the shims, and that was the problem
>> solved. So if you are lucky, whilst you might be getting
>> driven crazy by the problem as I am sure you are, it could be
>> something very simple.
>>
>> Regards,
>> K. Klika
>> ________________________________________
>> From: main_at_ammrl.groups.io <mailto:main_at_ammrl.groups.io>
>> <main_at_ammrl.groups.io <mailto:main_at_ammrl.groups.io>> on behalf
>> of CHARLES G FRY via groups.io
>> <https://urldefense.com/v3/__http:/groups.io__;!!BpyFHLRN4TMTrA!44tN59IuXMijRTo4YQUwV4s5PP6Uo-JihQ6B1TRjFDF--PbryU-vpNbFulfGuxyRy2EcePBb-jlJUk0Rd9mOo8Z41p95Vw$> <fry=chem.wisc.edu@groups.io <mailto:fry=chem.wisc.edu@groups.io>>
>> Sent: 16 August 2024 00:13:42
>> To: main_at_ammrl.groups.io <mailto:main_at_ammrl.groups.io>
>> Subject: Re: [AMMRL] Off axis shims bad after 24 hours on
>> 40-year-old Oxford magnet #Bruker #Hardware
>>
>> Wendy,
>>
>> More data helps. Other possibilities suggest themselves. One
>> possibility is your shim power supply being unstable. Stable
>> last night but back to fluctuating this morning. Intermitant
>> contacts to RT shims are another possibility. Large metal
>> objects are not being moved within 10-20 ft of the magnet
>> (including floor above or below)? Shim stack is loose and
>> moving a bit? Etc.
>>
>> Quenches are one way events. Once they happen a power supply
>> has to be attached to reenergize the main coil or cryoshims
>> coil. There is usually a period before the quench when
>> increased drift is observed.
>> Charlie
>>
>>
>>
>> On Aug 15, 2024, at 4:54 PM, Spin-Doc <bert.heise_at_spin-doc.net
>> <mailto:bert.heise_at_spin-doc.net>> wrote:
>>
>> Hi,
>>
>> Could you possibly specify “lineshape deterioration” a bit
>> more precisely? I mean, are we talking about a change from 1
>> Hz linewidth at half-height to something like 5-10 Hz (not
>> great, but can easily be induced by e.g. changes in the sample
>> like bubble formation, product fallout or solvent evaporation)
>> or 200-2000 Hz (making up numbers, but that’s what a failing
>> cryoshim can easily lead to)?
>>
>> A failing cryoshim is also one-way only, so lineshape is and
>> stays bad afterwards and an only rarely be compensated by RT
>> shimming. Your case doesn’t sound like a cryoshim effect to me…
>>
>> Best regards
>> Bert
>>
>> -> Sent via mobile <-
>>
>> Spin-Doc
>> Magnetic resonance equipment, service, training & more
>> Dr. rer. nat. Bert Heise
>> Owner, applications scientist
>> Kiefernweg 13
>> 58239 Schwerte
>> Germany
>> Web: www.spin-doc.net
>> <https://urldefense.com/v3/__http:/www.spin-doc.net__;!!BpyFHLRN4TMTrA!44tN59IuXMijRTo4YQUwV4s5PP6Uo-JihQ6B1TRjFDF--PbryU-vpNbFulfGuxyRy2EcePBb-jlJUk0Rd9mOo8bLDYpC5w$><https://urldefense.com/v3/__http://www.spin-doc.net__;!!Mak6IKo!OZtSmCHeEIYv6yibmvVZhQR-r8QAwcFdgWngD1EP6f4byErecGcIEFNCiVyw1eSYHPPRI9eM1c2AqgVqm-Hkkv0$ <https://urldefense.com/v3/__http:/www.spin-doc.net__;!!Mak6IKo!OZtSmCHeEIYv6yibmvVZhQR-r8QAwcFdgWngD1EP6f4byErecGcIEFNCiVyw1eSYHPPRI9eM1c2AqgVqm-Hkkv0$>>
>> Mail: bert.heise_at_spin-doc.net <mailto:bert.heise_at_spin-doc.net>
>> Phone: +49-171-5135315
>>
>> Representing MestreLab, Stelar & Barthel HF
>>
>>
>>
>> Am 15.08.2024 um 22:24 schrieb Wendy Breyer <web216_at_lehigh.edu
>> <mailto:web216_at_lehigh.edu>>:
>>
>>
>> Hi,
>>
>> Is it possible to have a cryoshim fail intermittently? I made
>> a full drift measurement over 13 hours last night as outlined
>> by Charlie Fry and saw very little drift AND very little
>> change in peak shape... but, on the same sample on other days,
>> I've seen peak shape degrade over a few hours ("lock" was on
>> though so I don't know if center position drift happened
>> during those data collections). In fact, a student used the
>> spectrometer this morning after me and saw large degradation
>> in peak shape over the course of his 1.5 hour experiment.
>>
>> Thanks for all your help!
>>
>> Wendy
>>
>>
>>
>>
>>
>> John Decatur Ph.D.
>> Director of Chemical Instrumentation
>>
>> Director of Precision Biomolecular Characterization Facility
>> 3000 Broadway
>> Department of Chemistry
>> Columbia University
>> New York, NY 10025
>> 212-854-2155
>> jdd13_at_columbia.edu <mailto:jdd13_at_columbia.edu>
>>
>> decatur.john_at_gmail.com <mailto:decatur.john_at_gmail.com>
>>
>
--
Dr. rer. nat. Matthias Brandl (he/him or they/them)
Technical University of Munich
TUM School of Natural Sciences - BNMRZ
Chair of Biomolecular NMR Spectroscopy (Prof. Sattler)
Lichtenbergstr. 4 (postal)
Ernst-Otto-Fischer-Str. 2 (physical)
85748 Garching b. Muenchen
Phone +49 89 289-52617
matthias.brandl_at_tum.de
https://www.sattlerlab.de/
https://www.bnmrz.org/
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