whitequark changed the topic of #tinyqma to: design of an open hardware DDS-based QMA with a low-voltage dc/rf stage :: http://irclog.whitequark.org/tinyqma
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<whitequark>
reitffili: o/
<reitffili>
hmm?
<reitffili>
o/
<whitequark>
you're @runefoams right?
<reitffili>
yep
<whitequark>
so a mass spec is pretty simple to make. you need a high vacuum system, a faraday cup and a quadrupole mass filter
<reitffili>
are those things, also simple to make?
<whitequark>
weeeeellll
<whitequark>
define "simple"
<whitequark>
you need access to a machine shop and around $2000, give or take
<whitequark>
fortunately, i have access to a machine shop and some cash that i can burn to collaborate with people on making instruments
<reitffili>
as simple as the list you described?
<reitffili>
so hypothetically what would one need to do if one did not have 2000 dollars or access to a machine shop?
<whitequark>
you can get the cost arbitrarily low if you're lucky in dumpster-diving at the nearest uni
<whitequark>
machining is a hard requirement though
<reitffili>
hardware is actually hard in difficulty?
<whitequark>
I wouldn't call it hard, but it's certainly a step above your typical arduino project
<whitequark>
you can probably go a long way with a laser cutter from a hackerspace
<whitequark>
for the actual mass spectrometer
<whitequark>
the envelope of the vacuum system is ideally machined from 316L stainless and TIG welded, which some hackerspaces can also assist with
<whitequark>
but like, in worst case it's probably possible to do something using stuff like copper plumbing fittings
<whitequark>
you do need a turbopump or a diffusion pump
<reitffili>
I had no idea mass spectrometers were so big, for some reason when I think meter I think about things that could fit in a hand?
<whitequark>
the actual mass spectrometer can fit in your hand.
<whitequark>
the vacuum systems are ... well... traditionally larger.
<whitequark>
that said you can make them compact BUT it'll cost you like $10k in used equipment
<whitequark>
the EXT70 turbopump alone is $3k used
<whitequark>
you can also make one that fits like on a half of your palm using some interesting advances in MEMS vacuum pumps
<whitequark>
well, you can't
<whitequark>
and I can't
<whitequark>
NASA can :p
<reitffili>
I guess its in how you use those things to make the spectrometer?
<whitequark>
ehhhhh, not really
<whitequark>
it's more of an accident overall I think
<whitequark>
with these low volume components cost is essentially irrelevant to size
<whitequark>
and performance is often more important than cost
<whitequark>
until recently no one cared about a small massspec, so it happened to be the size it was convenient to make in to meet a given performance target
<whitequark>
i think there's now a market for 'desktop' massspecs but you pay more for them or something
<reitffili>
what changed?
<whitequark>
I'm not sure exactly. I think they became more widespread in labs
<whitequark>
and it's just more annoying to service, deliver, use a larger instrument
<whitequark>
like you didn't have really good turbopumps until late 80s
<whitequark>
or sensitive detectors
<whitequark>
and the larger your rods are, the easier it is to detect the signal
<reitffili>
I'm having some fun immature thoughts.
<whitequark>
>what are some average performance targets for practical use?
<whitequark>
uh hm
<whitequark>
well for example the one i want will have a m/z range from 1 to 2000
<whitequark>
as for sensitivity it's "whatever comes out"
<whitequark>
generally an m/z rnage from 1 to 200 is the more sedate target
<whitequark>
but i want to try a novel-ish technique
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<reitffili>
what is the novel-ish technique, why is it novel, why do you want to do it?
<reitffili>
now I'm wondering how this is related to the topic of the room?
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<nortti>
:S this seems a "bit" too technical for me
<nortti>
seems really neat, tho
nortti has left #tinyqma ["Only in silence the word, only in dark the light, only in dying life: bright the hawk's flight on the empty sky. —The creation of Éa"]