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From: John R Walliker <jrwalliker@gmail.com>
Newsgroups: sci.electronics.design
Subject: Re: A better electron microscope
Date: Sun, 11 Aug 2024 15:50:03 +0100
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On 07/08/2024 08:29, Bill Sloman wrote:
> On 7/08/2024 3:02 pm, Jan Panteltje wrote:
>> Scientists revolutionize microscopy by reimagining the logic of imaging
>>   https://www.sciencedaily.com/releases/2024/08/240801142229.htm
>>
>> New method significantly reduces the time and damaging radiation used 
>> to image fragile specimens
>> Date:
>>    August 2, 2024
>> Source:
>>   Trinity College Dublin
>> Summary:
>>   Scientists have devised an innovative imaging method using 
>> state-of-the-art microscopes
>>   that significantly reduces the time and radiation required.
>>   Their work represents a significant breakthrough that will benefit 
>> several disciplines,
>>   from materials science to medicine, as the method promises to 
>> deliver improved
>>   imaging for sensitive materials such as biological tissues that are 
>> especially
>>   vulnerable to damage.
>>
>> And chips?
> 
> The paper claims "Giving microscopists the ability to 'blank' or 
> 'shutter' the electron beam on and off in a matter of nanoseconds in 
> response to real-time events has never been done before."
> 
> It isn't true. The stroboscopic electron microscopes that Cambridge 
> Instruments sold from about 1983 as electron beam testers could deliver 
> a half-nanosecond wide pulse of electrons.
> 
> The electron beam microfabrictors we'd been selling for year could turn 
> the beam on and off in less than 10nsec - I worked on the beam-blankers 
> for both.
> 
> Scanning transmission microscopes do use higher voltage electrons, but 
> that just means that the electrodes that blank the beam have to be 
> longer. With a half nanosecond wide pulse, you couldn't make the plates 
> too long for 2kV electrons because the transit time got longer than the 
> blanking period and I had to invent a solution to get around that, but 
> "a matter of nanoseconds" give you more wiggle-room.
> 
A bigger problem for biological tissues is that they have to be dried
before they can be put in a vacuum chamber and this process can distort
them.  They also usually need to be stained with a heavy element such
as uranium for TEM and coated with gold or other conductive materials
for SEM.
John