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

Fri May 29 06:38:28 EDT 2020

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.

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?
> 
> 
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> [External Email]
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> 
> 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
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>                                              
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> 
> 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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