Another School Year Begins

Yes, another school year begins. Students arrive ready to take on kinematic equations and vectors, linear momentum and fluids. They are ready to sit, packed into a 150 student lecture hall to learn about the beauty of physics - well, as I see it. But this is a naive thought. Most of these students are taking it because it is a prerequisite for their programs they are hoping to get into physical therapy or  medical school. The smaller group are physics, chemistry and computer science majors.  The question I always struggle with is how to keep the small group interested while still teaching to larger group what they need to know? I have to emphasize how important physics and critical thinking is to the pre-group while keeping it interesting to the small group who is already finds physics fun and hope they don't lose their enthusiasm in the subject. No, I am not alone in this task, professors all over the country struggle with this question but allow me this lament for one post.

All's quiet on the Kentucky front - except for that incessant beeping ....

As an experimental nuclear physicist, I must travel to laboratories with accelerators to perform experiments. Some people might not like this as they prefer to stay at home and sleep in their own bed and watch their kids play ball on the weekends.  I LOVE it. I have always loved to travel and that is one of the perks of being a physicist. Plus, I don't have much to worry about when I leave town, I have an understanding husband (which is a major help) and a Department who encourages my research.

This week I am at The University of Kentucky Accelerator Laboratory finishing up an experiment started a few weeks ago. Experiments are like flights - you want them to be as boring as possible. That means, everything is running smoothly. As soon as there is action, something has gone wrong and that is no good. If the machine is running well, the data is coming in and all the parts are in working order, experimental shifts are equivalent to watching paint dry. That is not the same as saying the experiment itself is boring, no way. The physics you are exploring, what you are looking for is very interesting, but you have to wait for the data to come in and then analyze it for months after the experiment has finished.

Experiments are never a solitary effort. Accelerators run 24 hours a day, every day as long as you have "beam on target". When the machine in on, someone has to be there to watch the machine, i.e. babysitting, to make sure nothing goes wrong. Preferable, you would like two people there for safety (what happens if one person falls and hits their head at 3 a.m.?) Not only do you have to watch the machine, but you have to watch that the data coming in and all of the electronics. The machine at UK is small and one person can be in charge of all of these things. Other places need someone in charge of just the machine (an operator) and someone in charge of the experiment.

This week, the we are looking into a problem discussed by Bohr and Mottleson in a 1975 work on nuclear structure. We bombard a target with neutrons and record the gamma rays which come out after inelastic neutron scattering. These gamma rays are detected with HPGe detectors like mentioned in GammaSphere. Unlike GammaSphere, we only use one in this experiment.  Van de Graaff accelerators have been around for a long time. The one at UK was installed around 1963 and underwent an upgrade in the 90s. What makes it special is the ability to produce a neutron beam which is done using a 3-He(p,n) reaction.

Why do I mention beeping? We monitor the accelerator by using a mechanical "popper" or beeper. This popper is hooked up to the beam current delivered by the machine and gives a sound to the current and therefore can be monitored. An ideal beam current is around 1.8 mA and if that is the case, "Tainted Love" can be sung to the popper. 

The control panel. Not much has changed since 1963.

I just like the sign.

My beautiful data coming in, it's beautiful.

The gift that keeps on giving.

When I was a Senior at Indiana University South Bend I went to my first Nuclear Physics conference. There are many things I remember about that meeting but one I was reminded about today while I was touring the Argonne National Laboratory facilities.

At this conference there was talk after talk after talk showing level schemes which went to very high spin, 30+ levels, 52+ levels. WHAT? I was working on 0+ states. They were showing Gammasphere data. The general public knows Gammasphere as the detector which turned a man into The Hulk. (I won't go into this) The nuclear physics community knows it as an amazing detector array, some of the younger students might not remember it much at all.

Gammasphere is a large array, consisting of 108 high-purity germanium detectors which detect gamma-rays (essentially light) after a reaction takes place. It completely surrounds the target and there is a place inside to put auxiliary detectors for additional capabilities. This device was revolutionary at the time is was launched and led to advancements in technology in our field with impact in other fields. With it's first run in 1993 the data taken led to hundreds of papers, countless Ph.D's and many advancements in the field.

I have never analyzed data from Gammasphere. In fact, today was the first time I had ever seen in "in the flesh". I spent my career hearing about it, reading papers about it, "Gammasphere" is part of our vocabulary. I spent years working on experiments in the old Gammasphere room at Berkeley. I used the Gammasphere codes to analyze my fission data. I have been trained by physicists who earned their Ph.D's from Gammasphere data.

And we are still using it!! All these years later, it is still in commission. The beams have changed, but there is still a need for a ball of 108 detectors. It is nice to know that some things are not thrown aside because they are old. Below is a picture of Mr. Gammasphere himself looking at his "baby". I wonder what he sees when he looks at it. Is it like a parent looking at their adult child and still seeing a toddler? Does he still see it bright and shiny and full of promise? Does he remember the excitement as the first peaks were observed on the screen when it was turned on almost 20 years ago? I hope so.

Gammasphere opened, so only half can be seen.

Standing in front of Gammasphere.

"Mr. Gammasphere" himself, looking at his baby.