Greetings Naizhong,

Are the bellows calibrated? Ours fell way off calibration frequently. Make
sure both sides are actually 0% and 100% open when the software indicates


On Thu, Dec 24, 2015 at 7:38 AM, ZhangNaizhong <[log in to unmask]>

> Hi Hagit,
> Thanks for your quick reply. You are right, the sensitivity decreased on
> both sides. Our box and trap currents in this Aug. are 0.60mA and 0.90mA,
> respectively, and graduated changed to 0.54mA and 0.96mA now. I will check
> the parameters on focus board. Hopefully it will be helpful.
> Cheers,
> Naizhong
> From: Stable Isotope Geochemistry on behalf of Hagit Affek
> Reply-To: Stable Isotope Geochemistry
> Date: Thursday, December 24, 2015 at 6:48 PM
> To: <[log in to unmask]>
> Subject: Re: [ISOGEOCHEM] Problems of MAT253 on clumped carbonate
> measurement
> Hello Naizhong
> I cannot say if these 2 problems are related. they seem unrelated but the
> timing of both being the same is suspicious. you do not say, but  I assume
> sensitivity is lost on both sample and reference side. if only on one side-
> then it is a capillary or bellow problem that is related to the bad zero
> enrichment. if both side, it is probably something else.
> We had similar and sudden sensitivity loss on a 253 used for clumped
> isotopes back in 2009. we would lose 30% of the signal suddenly, every 2
> months. cleaned that source and got it back. after 1 year we could not it
> get it back and sensitivity was going up and down like crazy. then we
> realized the the problem is electronic - a faulty x-focus board. to check
> it, change the focus setting by very little on each parameter and see if
> sensitivity responds strongly. the plate that responds probably means a
> faulty electronic part associate with it.
> how are your box and trap currents?
> hagit
> -------
> Hagit Affek| Associate Professor
> Institute of Earth Sciences
> The Hebrew University of Jerusalem
> Edmond J. Safra Campus
> Jerusalem, Israel.
> Phone: +972.2.6584654 | Fax +972.2.5662581
> mail address: [log in to unmask]
> On 12/24/15 11:35 AM, ZhangNaizhong wrote:
> Dear all,
> We are managing a MAT253 for CO2 clumped isotope since 2013. Recently we
> have faced two problems and need your kindly suggestions.
> *1. When we measured the same gas (e.g. OZT std gas) at sample and
> reference gas sides, D47 deviated from 0 per mil (e.g. 10~20 per mil). *
> We have asked this question in 2013, when we initially installed MAT253.
> During that time, we got many suggestions, and we follow the method to
> change the capillary. It worked quite well until this spring, and we could
> get ca. 0 per mil when we measured the same gas. However, it suddenly
> changed to ca. 20 per mil from this May when every other parameters were no
> difference except the sensitivity (see our second problems).
> During the past months, we have tried to washing/baking the capillary by
> flame and Helium, but it didn’t work at all.
> *2.About the sensitivity. *
> We faced the problem that the sensitivity of MAT253 decreased suddenly
> (when we set Mass 44 to 16V, bellow pressure changed from 65mbar to
> 85mbar), also in this May.
> About these two problems, we thought that they were caused by either the
> pollution in ion source, or the pollution in capillary, or both of them.
> Therefore, we would clean the ion source soon, as well as considering to
> change the capillaries from stainless steel to nickel. Does anyone has
> faced this kind of problems and may have any better suggestions?
> Thank you so much for the kindly help.
> Merry Christmas and happy new year.
> Cheers,
> Naizhong Zhang
> PD in Tokyo Institute of Technology

Andrew Schauer
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