Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A constant pressure flowmeter for extremely high vacuum   We demonstrate operation of a constant-pressure flowmeter capable of
generating and accurately measuring flows as low as $2\times10^{-13}$ mol/s.
Generation of such small flows is accomplished by using a small conductance
element with $C\approx 50$ nL/s. Accurate measurement then requires both low
outgassing materials ($<10^{-15}$ mol/s) and small volume changes ($\approx 70$
$\mu$L). We outline the present flowmeter's construction, detail its operation,
and quantify its uncertainty. The type-B uncertainty is $<0.2$ % ($k=1$) over
the entire operating range. In particular, we present an analysis of its
hydraulic system, and quantify the shift and uncertainty due to the slightly
compressible oil. Finally, we compare our flowmeter against a NIST standard
flowmeter, and find agreement to within 0.5 % ($k=2$).

37
The categories of this paper are: supr-con
16
The categories of this paper are: stat
2
The categories of this paper are: math
28
The categories of this paper are: alg-geom
1
The categories of this paper are: cs
0
The categories of this paper are: hep-ph
11
The categories of this paper are: hep-lat
8
The categories of this paper are: hep-ex
32
The categories of this paper are: atom-ph
29
The categories of this paper are: funct-an
22
The categories of this paper are: chao-dyn
23
The categories of this paper are: solv-int
26
The categories of this paper are: bayes-an
9
The categories of this paper are: nlin
14
The categories of this paper are: math-ph
21
The categories of this paper are: adap-org