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Subject: Re: Using diffusion pump systems for ARcoatings

Date: 08/21/02 at 9:55 PM
Posted by: Pat McMahon
E-mail: film.vac@verizon.net
Message Posted:

In Reply to: Re: Using diffusion pump systems for ARcoatings posted by Hemang Jesrani / Astro Optics Pvt. Ltd. on 08/21/02 at 6:00 AM:

Hermang,

I see that there have been some answers to your query that seem to think that diffusion pumps are OK for your application and I would agree that diffusion pumping systems can be used successfully to produce your coatings. I have designed a few in my day. But if you look at all those answers, you will see that each one has a "but". By that I mean that they all say diffusion pumping is good "but" you have to watch backstreaming, foreline pressure, etc, etc.

I say you have had good results with turbo systems and you are familiar with them so why should you change to something different and perhaps bring a lot of problems into your process that you have not experienced before.

I run a production coating facility and I am thankful that I do not have to put up with all the problems that diffusion pumps can cause. And this is after many years of working with and designing diffusion pumped systems. It is hard enough keeping film properties in spec without the added problems of backstreaming, foreline pressure, oil contamination, Ln2 baffles, and a dozen other things that diffusion pumps need.

Good luck to you.

Pat


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