A bit about JLab

On Friday Sarah Phillips gave an overview  of Jefferson Lab and what a Hall C Physicist is. Here's just a bit more info on the accelerator, and some stuff about the Hall we work in.

The continuous electron beam accelerator facility is responsible for producing the high energy wave electron beam used in scattering experiments. An injector produces an electron beam at close to the speed of light, which circulates the ⁷/₈ mile track in 24 millionths of a second. Each superconducting linear accelerator (right) increases the beam’s energy, while magnets in the arcs steer the electron beam from one linac to the next for up to five “orbits”. The beam travels through the same linac on each orbit, but travels along separate beamlines in the arcs - this is because the magnetic field required to bend the beam depends on the energy of the beam. 

 After the final orbit the beam enters the switchyard and is delivered to one of three experimental halls for simultaneous research by three teams of physicists. Each hall has different detector capabilities, and efficiently allows different research to be done using the same beam.

On the left is a nice schematic “birds-eye-view” of Hall C. The beam enters the hall and is focused onto the target in the scattering chamber. During my experiment we used the Short Orbit Spectrometer (SOS) and the High Momentum Spectrometer (HMS) to detect scattered particles. Both spectrometer arms can vary their momentum and angular settings so we can get data at a range of kinematics. This is what Hall C really looks like inside -->

 

Everything is monitored and controlled in the Hall C Counting House, that’s where we go when we’re on shift. The one night I was on duty it snowed, which is quite rare for Virginia. Anyway, I ran outside and made a snowball and brought it back inside to take a photo. I wasn’t smiling so much later on at midnight, however, when it was still snowing and I had to cycle back to my room at the Residence Facility (right).

 

Finally, our Hall C mascot is this cute little monkey, who watches over the counting house and makes sure that we all behave :D

 

Comments

[Neil]

Thanks Claire,
Great explanation. I have always wondered what went on at Jlab.
N

[claire]

Hi Neil

Thanks for the feedback :) it's so nice to hear from the people reading the blogs. The Hall is very versatile when it comes to experiments, so every one is different. In a later post I'll talk more about my J/Psi experiment and how it fits into Hall C.

~claire

[Tommaso]

Hi Claire,
thanks for your visit... And for the pictures above!
Is that a heart you're holding there ?
And, what do you do with your J/psis ? How many ?
We're sitting on quite a few of them ourselves here in CDF...
Cheers,
T.

[Sarah]

That picture of Hall C does not look quite right... It does not have nearly enough physicists moving around equipment, technicians craning huge things around, and enormous piles of green shielding blocks surrounding the G_zero detectors! :D :D Did you get to see the G_zero detector array while you were at Jlab?

Talk to You Later,

Sarah

[claire]

Hiya

T - LoL no the snowball wasn't meant to look like that, but now that you mention it... Well I couldn't feel my hands okay!

J/Psi's in a nutshell, well we didn't get any! Okay, so it was sub-threshold but we were counting on the Fermi momentum of the nucleons to at least give us some. Still, it puts a nice upper limit on the cross-section. I'm going to have to write a post about this very soon I think!

Sarah - yeah the Hall was pretty empty most of the time. Generally they only opened it when we had problems, and we were running an almost 6GeV beam at 80 muA so there was a lot of radiation about too, so that's probably why. I did get to take a short peek round the back of the green blocks at the G0 detectors though, they looked very cool :)