The tube has gone bad in our ancient Sargent-Welch 623A specific charge
of the electron (e/m) apparatus, and replacements are apparently no
longer available. Being one of the few atomic & nuclear physics labs
that are practical in a small lab, I'd like to continue to do this lab,
but that means I'm in the market for a new apparatus.
VWR-Sargent Welch seems to be the main supplier these days, and they
offer several units from which to choose. I have experience with only
one of these, so before I sink a lot of equipment funds into one choice,
I would appreciate feedback (pro or con) from any of you who have used
any of the others.
Nakamura (CP32509-00) I used this unit at another institution, so it is
the only currently-available model with which I have any experience. It
gives very good results, but runs $1 550 each and still requires
external power supplies and external meters.
Daedalon (WL0623C) This has a similar design (horizontal tube) to the
Nakamura but the required power supplies are built into the base. It
also has digital meters built in. Even with these features, it costs
only $200 more than the Nakamura ($1 766).
Pacific Scientific Supplies (CP33892-00) This unit has a vertical tube
with power supplies built into the base. The main difference between
this and the Daedalon seems to be analog instead of digital meters and
detachable external scales. It also has a much lower price tag ($990).
I'd expect lower precision due to parallax error from the external scale
and perhaps the analog meters, but IMO, this adds some valuable
instructional opportunities, too. Do any of you have experience with
this device? Is it reasonably reliable?
CENCO (CP71267-00) This uses a SMALL vertical tube with an internal
circular scale. It requires an external power supply and meters. I'm
inclined to think that it isn't worth the price ($1 220 for the unit,
$709 for a replacement tube). Are there good reasons for me to think
Tel-Atomic (CP32054-00) This uses a horizontal electron gun and a tube
that is intermediate in size between the Cenco and the Daedalon/Nakamura
units. It also requires external power supplies and meters, but still
costs 1 625 for the unit, $779 for a replacement tube.
Given that I'd have to coordinate schedules and borrow high voltage
power supplies from the electronics lab, I'm inclined to think that
either the Daedalon or Pacific units would be my best bets. Do any of
you have experience with either of these units? If so, any constructive
reviews and suggestions are appreciated.