March Meeting observations

This year, I only went to the first three days of the March Meeting; extended trips are less feasible now with a baby at home. The trade show and posters are only Monday–Wednesday, and a fair number of attendees–particularly college faculty with classes to teach–stay for only a few days. So Thursday and Friday the conference is sort of a ghost town, but one thing I’ve heard from quite a few people this year is that it looks like several interesting sessions are scheduled for Thursday and Friday.

To read up on some of the physics presented at the March Meeting, a physics blogger’s account starts here. Physics journalists are blogging from the meeting here. Another attendee’s take is here. (I’ll update periodically if I find new blogged accounts.)
Photographing Talks
One phenomenon that’s becoming more common, and which is at least slightly disturbing, is for audience members to use digital cameras to photograph all the slides that a speaker presents. It’s obnoxious when the camera makes faux-shutter sounds, and it’s really obnoxious when the flash fires. When the flash is used, it’s also a sign that the photographer is an idiot, because the flash will make the image of the projected slide come out worse: physicists should be able to figure this out. If the photographs are unobtrusive, I haven’t quite figured out what the ethics of the situation are. I’d think if you really wanted someone’s viewgraphs, or data, you should just send them an email and ask: I’d share my data and graphs if someone asked for them.

Viewgraphs
I saw 39 talks this March Meeting, and only one used viewgraphs, and that was after the speaker attempted to use the computer but had some difficulty getting the computer to cooperate with the projector. The APS recommends that speakers have viewgraphs as backups; most don’t, but this speaker did, and the talk otherwise went off without a hitch. One out of 39 is 2.6%, which is a smaller fraction than last year (but not significantly so).

Microphones
One piece of technology that number of speakers decided to do without was the (supplied) wireless microphone, which is a real shame. Perhaps the folks up front can hear the speaker fine, but there’s always a background rustling of papers and backpacks and schedule books, and people are talking outside the room, and if the doors are open this really filters in, and if the doors are closed then they keep opening and closing as people straggle in. It’s really hard to hear an un-miked speaker in the back of the room.

Seating
Because of the 39 parallel sessions, in which you wish you could be two or three places at once, people do lots of session-to-session shuffling. It’s always awkward to squeeze in to the open seats mid-session. The solution to this: more aisle seats! Instead of having two columns of seats, with an aisle down the middle and sometimes aisles down the sides, the APS should have the convention center arrange the seats to be at most 4 across, in 3–5 columns, so that everyone who wants an aisle seat–which is everyone who’s shuffling between sessions–could get one. It would cut down on the capacity a little, but although there are some overflowing sessions, there are plenty that are sparsely attended. To this end, the APS should try a little harder to predict the attendance at the sessions, and put the popular ones in the large rooms. I know this is hard, but isn’t this the sort of problem that physicists should be able to tackle?

New Orleans Convention Center
The March Meeting isn’t like a trade show, where you need lots of floor space, preferably contiguous, for all the vendors to set up their booths. Rather, we need lots and lots of meeting rooms. Convention centers, as a rule, have both, but some do the meeting rooms better than others. The shorter the distances between rooms, the better, because at the March Meeting it is common to try to shuffle between different rooms during a session. In New Orleans, there were two giant rooms on the first floor, and the rest were on the second floor. Most of these were along one long linear corridor, but a handful of rooms were in a parallel corridor on the other side of the center. To get between these corridors you went through an elevated walkway that overlooked the trade show floor. The convention center is along the Mississippi river. Between the center and the river are active railroad tracks. In the rooms on the river side, one could clearly hear the horns of the trains that used this track. I suppose this isn’t a problem inside a noisy trade show floor, but when you’re trying to listen to a talk, it makes you wonder why the architect didn’t specify more robust soundproofing on the walls that face the river.

The trade show:

And the posters:

The PAR 124 lives!
Perhaps the most exciting development, from my perspective, was the unveiling of the Signal Recovery 7124 Lock-In amplifier, so new it doesn’t appear on their website. Lock-in amplifiers are one of the most useful pieces of equipment in experimental physics research: They perform frequency selective signal detection and amplification, showing the amplitude and phase that appears on a signal in relation to a reference signal. They are tremendously valuable for processing noisy signals.

Years ago, a company called Princeton Applied Research (PAR) produced a truly amazing lock-in, the PAR 124. Built with all analog electronics, and mostly from discrete components, it was very sensitive, very quiet, and had been a staple of low-temperature research labs for decades. Contemporary lock-ins are, as a rule, digital, making use of Digital Signal Processing (DSP) to process the input signals, and do more with them than ever possible with analog electronics. But the digitization process itself is noisy, sending a sort of switching noise back up the input line to the experiment. This added noise and energy is very much unwanted in low-temperature experiments, so low-temperature labs kept PAR 124s around and sought them out from second-hand equipment dealers.

(I’ve used them in many of the mechanical oscillator projects I’ve worked on, but for a slightly different reason. Even when you use an external signal for the reference channel of the 124, the internal oscillator locks to your external reference and then this internal oscillator is used for signal processing. Because of the way this locking is accomplished, the 124 can be used to implement a phase-locked loop, by driving the mechanical oscillator with the reference signal output.)

Princeton Applied Research was bought by EG&G, who was then bought by Perkin-Elmer, then became Ametek, and who finally decided to call themselves Signal Recovery. And whenever they showed up at a trade show, such as at the March Meeting, low temperature physicists (including myself) would always ask if the PAR 124 would ever come back. “We’re working on it,” was always the answer.

And so they were. This March Meeting, they had on display the 7124 lock-in. It uses an all-analog front end, to which you connect your experimental signal. It’s connected by a 5-meter fiber optic cable to a digital DSP lock-in, so you can take advantage of all the advanced features of a DSP lock-in without the digitizing noise getting back to your sample. If I had a spare $15000 sitting around, I might buy one.