[labnetwork] Hazard due to x-ray production in e-beam evaporators?

Fri May 29 11:11:06 EDT 2020

Dear colleagues,

Thank-you all for the excellent discussion and suggestions—this has been
incredibly helpful.  Beyond allaying the fears of the user who raised the
concern, going forward, we will be sure to incorporate an explanation of
these considerations when training users on our evaporators.

Stay safe and healthy.

Cheers,

 – Aaron

Aaron Hryciw, PhD, PEng

Fabrication Group Manager

University of Alberta - nanoFAB

W1-060 ECERF Building

9107 - 116 Street

Edmonton, Alberta

Canada T6G 2V4 Ph: 780-940-7938
www.nanofab.ualberta.ca

On Fri, May 29, 2020 at 4:38 AM Stephen Howe <info at fabsurplus.com> wrote:

> Dear Aaron,
>
> I used to work on Mass Spectrometers for VG Analytical, which became part
> of Thermo Instruments eventually.
> They had a low accelerating voltage of 8KV, but we had some tools with a
> FIB option installed (Fast Ion Bombardment), and that operated at up to 16
> KV.
> We had a viewport above the source area, so as to have a reality check on
> what was really going as one poked around inside the vacuum chamber. The
> viewport had leaded glass. This might be erring on the side of excessive
> caution, but such view port glasses are readily available for purchase in
> the market place, so that's what I'd suggest.
>
>
> --
>
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> On Thu, 2020-05-28 at 13:48 +0000, Robert Vandusen wrote:
>
> Hi Aaron.
>
> Back in 2015 we had similar concerns with our Balzers BA 510 thermal/ebeam
> evaporator.   We had reintroduced thermal capability to our system and had
> modified our internal SS shielding to allow us to have a direct line of
> sight to the thermal melt through a glass slide mounted on the shield and
> through one of the window viewports. Prior to this we only used ebeam
> evaporation and the shielding blocked the viewport.    As you have found, I
> was unable to find any literature on x-ray exposure concerns outside the
> chamber area.
>
> I contacted our Health and Safety department who helped conduct x-ray
> testing during ebeam evaporations of a few different materials.   They
> found no measurable x-rays coming through the viewport or elsewhere on the
> chamber.  This satisfied our safety concerns.  However since the system was
> now identified as an potential x-ray producing source we had to get an
> Ontario ministry of labor x-ray permit and post it at the room doors and on
> the system.  It basically requires us to get a new assessment if we make
> any changes or modifications to the system that could result in increased
> exposure.
>
> So we have piece of mind, but now a lot more questions when users see the
> x-ray signage.
>
>
>
> Hope this helps.
>
> Rob
>
>    Robert Vandusen
>    Microfabrication Cleanlab Facility Manager
>    Electronics Department
>    Carleton University
>    room: 4184 Mackenzie Building
>    613-520-2600 ext 5761
>    Robert_vandusen at cunet.carleton.ca
>
>
>
>
>
>
>
> *From:* labnetwork-bounces at mtl.mit.edu <labnetwork-bounces at mtl.mit.edu> *On
> Behalf Of *Aaron Hryciw
> *Sent:* May 27, 2020 11:21 PM
> *To:* labnetwork at mtl.mit.edu
> *Subject:* [labnetwork] Hazard due to x-ray production in e-beam
> evaporators?
>
>
>
> [External Email]
>
> Dear colleagues,
>
> One of the users in our open-access facility recently expressed concern
> about x-ray production in electron-beam evaporation systems.  Since the
> typical acceleration voltage in our e-beam systems is 7–10 kV, he was
> concerned that bremsstrahlung and characteristic x-rays would be generated
> during deposition, with a maximum energy of 7–10 keV (soft to hard x-rays),
> and that these x-rays would pose a health and safety hazard to an operator
> standing next to the viewport for ~30 minutes.
>
> A literature search yielded a few reports describing radiation damage to
> sensitive devices from x-rays produced during an e-beam metallization step,
> but I did not find any mention of related health and safety
> considerations.  While some x-rays are undoubtedly produced, presumably
> there are reasons why they are not hazardous to an operator (e.g., perhaps
> total x-ray output is very small, majority of x-ray spectrum is low energy,
> x-rays do not penetrate stainless steel chamber walls or viewport windows,
> etc.).  I would like to answer this user with specific physical arguments
> as to why the hazard is insignificant, however, so any advice you could
> offer to this end would be greatly appreciated.  Many thanks.
>
> Cheers,
>
>  – Aaron
>
>
>
>
> Aaron Hryciw, PhD, PEng
>
> Fabrication Group Manager
>
> University of Alberta - nanoFAB
>
> W1-060 ECERF Building
>
> 9107 - 116 Street
>
> Edmonton, Alberta
>
> Canada T6G 2V4 Ph: 780-940-7938
>
> www.nanofab.ualberta.ca
>
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