10/3/97

I would be interested to hear from other SEM users with the same (JOEL

JSM 5400) or a similar SEM what sort of filament life you are achieving

?

I fear that we may have a vacuum leak since the filament life is

characteristically low and tarnishing is usually visible on the filament

holder. The latter I am told may be an indication of a vacuum leak in

the system.

Regards

J. Paetz (Senior mineralogist)

Amplats Research Center

Republic of South Africa

JPaetz@amplats.co.za

You are correct that a discolored base is usually a sign of a poor

vacuum. A normal burnout of a filament should have a bubble on top of

the broken wire. If your filament burns out this way and the base is

discolored it is probably a bad vacuum. If the filament is craked , no

bubble, then their could be a flaw in the wire or a slight crack was

made by human handling.

We do not use a JEOL ourselves, but we do sell filaments for all the

different scopes and our customers seem to feel you should get 50 - 200

hours out of a filament.

John Arnott

Ladd Research

ladres@worldnet.att.net

I have the same machine as yours with selected operation for low vacuum

chamber (JSM-5400LV). For high vacuum operation, more than 100 hours,

sometime 130 hours of filament life can be achieved.

******************************************

Zhiyu Wang

Electron Microscope Lab and Imaging Center

Western Kentucky University(WKU)

Bowling Green KY 42101

Phone: (502)745-5993(office)

email: wangz@pulsar.cs.wku.edu

I work on a CamScan SEM/EDX and have lifetimes from 90-240 hours,

depending on how much EDX (20kV, SEM: 15kV) I made. The lifetime of the

filament does not seem to depend on the sort of the filamnet, cheap ones

have similar lifetimes to more expensive ones.

Our SEM has no lock, so we have to ventilate (with N2) the whole column,

including the filament.

Greeings, O.Rother

--

Oliver Rother

Institute for Geology and Paleontology

Scanning Electron Microscope (SEM)

University of Kiel, Germany

Tel. +49 431 35021

Fax: +49 431 35262

stu33845@mail.uni-kiel.d400.de

Filament life is a function of many factors. The presence of tarnishing

usually signifies some sort of oxidation, implying a vacuum leak. I must

say, if your SEM is a new one, that filament life usually improves over

the first year of life. I think this is a result of outgassing the whole

system. BTW, if you have a "bubble" at the end of your burnt-out

filament, this is a result of over-saturating the filament. Remember to

check the satuation level every hour for the first six hours of a new

filament's life, as the saturation level drops fairly quickly, then levels off.

After the second year, a filament lasts me a month.

I do not have a JEOL 5400, these are just general W-filament comments.

Mary Mager

Electron Microscopist

Metals and Materials Eng., UBC

6350 Stores Rd.

Vancouver, B.C. V6T 1Z4

CANADA

tel:604-822-5648, fax:604-822-3619

e-mail: mager@unixg.ubc.ca

150-200. We feel that is low. Our JEOL 733 filiments last in the 1000's

of hours. The 5800 burnt filiments display the small "ball" (normally only

present on one end of the break unless the filiment has been very

over-driven). The bases of the filiments are always slightly discolored

and we do not have a vacuum leak (that we know of). The bases may get

discolored when we work in LV mode (though I have been assured that the

vacuum in the gun chamber stays very high). Our JEOL 733 filiment bases

are always somewhat discolored, and we watch the gun chamber vacuum very

closly, so I know there is no leak.

One thing that may extend the

filiment life is allowing the filiment to cool before venting the chamber

(I don't know if the 5400 uses an exchange port or just vents the

chamber). On our Hitachi S-450 we found that doing this does increase

filiment life, but the 5800 is new and we have just started cooling the

filiment, so I do not know what the effect will be. I do know that

machines that change Acc kV on the fly have shorter filiment lives.

I write this not to contradict John Arnott's above statement, but just to

show that there are "extreme" differences in machine filiment lives that

are not just based on the type of machine being used but also possibly on

the way the machine is used. The number 50-200 hours seems low to me, but

most of my experience is on the 733, so maybe I am spoiled. As far as

discoloration being a sign of a leak, I bet it is, but how much

discoloration is normal should also be a question.

I hope someone got something useful out of that.

Christopher

Institute of Meteoritics

Albuquerque, NM USA

ladres@worldnet.att.net