Debbie Harris

So THAT's a laser tracker!

April 29, 2005

Language is a funny thing:  you can hear a phrase over and over again and think you know what it means, but then if you see an actual demonstration you realize it's much more interesting than the simple words can lead you to believe. 

Part of setting up the NuMI beamline involves putting in lots of detectors up and down the line that measure the position of the proton beam very accurately.  If you think about how you might do that, you realize that you have to first know how the detector works in the first place to measure a position in its reference frame, but then you have to know exactly where that detector is sitting in your beamline, since the detector itself can't tell where it is at all. 

The job of measuring where all these detectors are exactly in the beamline belongs to the Alignment and Metrology Group at Fermilab, and they have all kinds of bizarre tricks and devices whose names don't really do justice to how cool these devices are. 

Last week I got to see something in action that I've heard of over and over again but never seen:  a laser tracker.  This thing is a laser that really can follow the motion of a little ball that has a mirror on it--the surveyor with the steadiest hands (at the left) holds a ball with a precision post on the end of it and sets the post in one of 4 holes that are drilled into a plate attached to the detector in question.  The laser tracker itself looks like a person watching a tennis match:  it watches the ball, then occasionally swings back to look at some reference point, then swings back to watch the ball. 

But of course it's not enough to just watch the ball...Once the post is sitting in its hole then the surveyor says "okay" and his partner in crime (in the orange vest at the left) clicks a button on a special computer nearby, and that's how the measurement is taken (I think):  The computer calculates how much time it takes the light to get from the tracker to the mirrored ball and back, and then it knows the position of that ball on that post to a rediculously high precision (1/1000 of an inch!).  The computer can even set up a "watch window" to tell you exactly how much you might have moved this ball between now and the last time the surveyor with the steady hands said "okay". 

The detectors that we're doing extra tests on, BPM's, measure the position of a proton beam without ever interfering with it--they work because the charge on the protons induces charge on two half-cylinder plates that make up the BPM.  We are doing extra tests on the spares to make sure we understand the ones that are in the beamline.  The way you test a BPM is that instead of having to send a beam of protons through it, you just send a wire with current through the BPM, see what the signal is that gets induced on the two plates, and then move the wire around. To the left is the BPM expert looking at the induced signals.  If you're really lucky you have the surveyors checking that you moved the wire just as much as you thought you did. 

It's funny, as exciting as it's been to be in one control room or another and look at computer screens that tell you what the beam is doing, there's a risk of feeling remote from the devices that are actually doing the measurements.  It was good to see these tests happening first hand and to get a feeling for what goes into making sure everything is in the right place. 

What I take for granted...

April 26, 2005

I am doing a lot more explaining what I'm doing these days to people outside the field of particle physics, and as a result I'm learning that the things that I take for granted are often the most interesting things of all to people who are not in this field. 

For example, someone once asked me whether or not I use Einstein's theories of relativity in my work--the first thing that came to mind was the fact that most of the particles I deal with are travelling very close to the speed of light.  This means that the particles that decay to neutrinos seem to be decaying much more slowly than they would be decaying if they weren't going so fast.  In fact I'm so used to dealing with relativistic particles that I sometimes get in trouble when I try to think about what they do when they slow down! 

I spoke to a troup of girl scouts visiting Fermilab 2 weeks ago, and the thing that they were really amazed by was the idea that you could shoot a beam of neutrinos through the earth and they would just pass through and keep going forever into outer space.  I explained how we have these neutrinos that can get from here to Minnesota in just 2 and a half thousandths of a second (which in itself is a hard unit of time to understand).

Sure enough one girl asked if we could even shoot a beam of neutrinos through the middle of the earth (you can almost see this on the white board at the left of the picture shown here).  She seemed surprised to find out that plenty of folks around the world are actually thinking about what kinds of things you could learn about neutrinos, or even what you could learn about the middle of the earth by doing such an outrageous thing! 

Although I take for granted the fact that neutrinos could pass even through the core of the earth and not even notice, I certainly don't take for granted how hard it would be to build the beamline.  Imagine a half mile tunnel that points straight down, which lets all those pions decay (ever so slowly because they are relativistic).  But maybe by the time these girl scouts are designing their own experiments, that's where they will be aiming. 

Following in the Footsteps

April 22-23, 2005

Saturday night was the first night of Passover, and since I have the biggest dining room table between my mother, my cousins in Chicago, and myself I hosted a seder (dinner party that involves telling the story of the Jews leaving Egypt).  Ever since Isaac was born (8 years ago), I have hosted a seder each year. 

Preparing for the seder is always an introspective time for me--I keep thinking of all the seders when my mother, grandmother, and I would do all the standard tasks like peeling potatoes, peeling apples, peeling hard-boiled eggs...come to think of it the holiday preparations are about 90% peeling.  This year my grandparents stayed in Florida and my mom had a cast on her wrist, so it was just Isaac and Sonia helping me getting ready for Passover. 

Both Isaac and Sonia really wanted to peel potatoes and cut them up with sharp knives, and I think the preparations were a success given the fact that no blood was shed. I had this revelation though about time passing:  when I was a little girl I would always marvel at how quickly my mother and grandmother could peel potatoes compared to me, and on Friday night I got to see Isaac marvel at how fast I can peel compared to him (but I should add here that my mother and grandmother still win hands down in peeling speed).   

I am slowly but surely getting used to running a seder though.  It's funny how the idea of my doing physics (when my dad is a physicist) was much easier for me to accept than the idea of my running a seder (given that my dad or grandfather ran most of the seders of my childhood).  But now that I think of it, Isaac and Sonia are probably growing up expecting that women are more likely to run the seders! 

A Day in the Life...

Yesterday I received an email asking if I would write a blog about what I did on April 15, the "World Day of Science" which shows what a "typical" day is like for a physicist.  Since no two days ever seem to be alike, it's basically impossible to say what  typical day is like.  Nevertheless I have outlined the day.  Although certainly most of my days don't involve this many meetings, they do involve trying to do very different things on at least two very different experiments in rapid succession.  So at the risk of painting a not terribly glamorous picture of a day in the life of one scientist in particular, here goes...

April 15, 2005

6:30AM Wake up, shower, put breakfast on the table (4 bowls, 5 kinds of cereal, two kinds of milk:  Organic and not organic, and one kind of coffee: strong French Roast). 

7:00AM Phone meeting with Kevin to talk about MINERvA funding requests--Kevin leaves on vacation today so it's our last chance to talk about this before my big meeting with the head of the Particle Physics Department next Wednesday to ask for money...it's easy to be impatient and think "why can't we just build this detector and do the experiment now, the neutrinos are already here!" but all this takes money and planning so that's where we are on MINERvA. 

7:45AM The kids are up so the meeting is over and I get Sonia dressed and we all eat breakfast together.  Unfortunately Rob (their father) is going through a Johnny Cash phase and as a result so are Isaac (who is 8) and Sonia (who is 4).  So breakfast music is "Burning Ring of Fire" and "A Boy Named Sue" both of which Isaac and Sonia sing loudly and even approximately in tune. 

8:20AM Leave the house with both kids.  I drop off Isaac at his school first, two minutes later.  Isaac really likes the "Before and After School" program at his school so he actually wants to go there early even though in principle Rob could drop him off at 9:05 when his regular school opens their doors.  Here is Isaac signing in for the Before School program. 

8:50AM Arrive at the Fermilab Children's Center after a drive in the car with Sonia.  Although I don't have Johnny Cash in my car, I do have a children's CD that has Sonia's name sung repeatedly which she insists on hearing.  She also likes to read in the car, something she certainly didn't inherit from me.   

8:53AM Sonia is ecstatic because she sees that today is her turn on the computer (along with two other kids).  That child can sit and play games on the "pewter" for hours, no matter how much I tell her that your brain doesn't grow when you do that. 

9:00AM Walk into the 15-story building where my office is.  Go to the Medical Office on the ground floor to get a tetanus shot.  I stepped on a thumb tack two days ago, and am finally getting around to getting a shot.  This was prompted by my mother calling me last night and telling me I should get a shot and to send her email the second I got one so that she could stop worrying about me and move on to something else. 

9:30AM--Arrive in my office with a sore arm.  Getting the tetanus shot took much less time and effort than I thought it might take!  Read and answer email for roughly an hour about lots of different topics. 

10:30AM  First of today's four meetings--this one is to discuss several different detectors that measure the proton beam along the NuMI beamline before it hits the target to make (eventually) the neutrinos.  The detectors are installed and we've seen real beam and it's clear they work, now we are focusing on the details of precisely what their measurements mean.  We talked mostly about two different kinds of detectors--how do we know exactly how many protons hit our target on any one shot, and how do we know exactly how much "spray" from that beam hits other stuff before the target?  The "toroids" and the "loss monitors" tell us each of these things, but we have to be able to interpret their signals correctly!  This means calibration...

12:00 Ten minutes after my last meeting ended, the next meeting begins:  this time it's a MINERvA phone meeting--many people are calling in to a conference call and those of us at Fermilab sit around one speaker phone to all talk to eachother.  Today's meeting was about studies people are doing to show how much more or less physics we could do by making the detector more or less sensitive (which means it would cost more or less money).  I think I'm the fastest typer in the collaboration, so besides being the project manager I"m also the one typing the minutes during the meeting...

This meeting room has a great view, identical to the one from my office (since it's right next door). 

1:15 Two meetings down, two to go:  run downstairs to the cafeteria to buy a sandwhich and grapefruit juice for lunch.  I'm too embarrassed to take my camera to the cafeteria...so you'll have to imagine this on your own.  For exercise I walk the 12 flights back upstairs to my office and eat lunch while looking at MINERvA budget sheets. 

2:00 Meeting to discuss a new "World Design Study" (funny name, isn't it?) whose goal is to get people all over the world to participate in a new design for something called a neutrino factory.  It's a concept people have been studying for awhile now which involves making a neutrino beam in a totally different way:  instead of focusing pions and letting them decay to neutrinos, you somehow make and focus a beam of muons, accelerate them to very high energies, and then let them decay to neturinos...it's a very different beam from what we're used to, and might be very very powerful, if only people can figure out how to make one!  The meeting was specifically to talk about what kinds of funky detectors might we want to develop in the future to make measurements with this new beamline.  Although we had a very interesting discussion in this meeting, by the end of it I was getting pretty tired of being in meetings all day...

3:15PM  One more meeting, although this one hardly counts since it's with Jorge (pictured above in the MINERvA meeting) and it's just the two of us going through the budget request we made for MINERvA earlier this year and figuring out how much more money we'll need to ask for to cover everything we need to pay for in the very near future.  We have submitted a few proposals for funding to other places (National Science Foundation and the Department of Energy) and although they all like the idea of the experiment they all write back and say they think we should get the money through Fermilab instead.  It sort of feels like the rules are changing under our feet, but on the other hand the lab is being more supportive of getting this experiment off the ground than it ever has been before.  It's great to be in the position where I'm figuring out how much we really need, as opposed to trying to convince people we should build the experiment in the first place!

4:45PM Leave early to get Sonia at day care--it's a beautiful day and I wish I had been outside for even a small fraction of it!  Sonia is playing outside with her friends and I"m thinking it's a good thing the weekend is here and I'll be outside a bunch tomorrow.  On the drive back home Sonia forgets to ask for her CD and we get to listen to Jazz on Public Radio instead. 

5:20PM Pick up Isaac at the After School program where he's been playing outside too.  Sonia immediately runs into the room to play with the big kid's toys, though. 

5:50PM Arrive at the Noodles and Company restaurant after changing into our "Temple Clothes" for services tonight.  We eat a very quick dinner, unfortunately:  something else I'll have to make up for over the weekend. 

6:35PM Arrive at the synagogue 5 minutes late for "Tot Shabbat", which are services designed for infants up to ~7 year-olds.  It's a lot of singing and the Rabbi tells funny stories, and the kids at least get into the hang of going to services and taking time out to do something different on Friday nights.  (These kiddy services are only held once a month)

7:00PM  Hit the "oneg", which is in this case another word for bribery to get your kids to sit through services: it's a low table with a bunch of cookies on it in a room that is also used for a preschool at the synagogue.  The kids all play together with the various toys and the adults all hang out and chat.  I talked with a few women about growing out of bridesmaid dresses, and how people on planes can be very unsympathetic to travelling babies. 

7:30PM Leave the Temple, and stop by Trader Joe's to pick up a few groceries for tomorrow:  I'm having a dinner party with two friends from grad school and their families--but that's a subject for another day. Isaac and Sonia go nuts picking out "drinky yogurts" and plums, but I am too tired to protest that we don't need that stuff right now.

8:00PM Finally arrive at home, talk to my dad on the phone to find out what my mom is worrying about now since I got my tetanus shot this morning. 

8:30PM Start getting the kids ready for bed:  put on pj's, brush teeth, and read them a story:  tonight it's the Bearnstein Bears Count Their Blessings.  My kids love this series (especially Sonia) and although it's way preachy it is all stuff I would be preaching myself if I thought my kids would listen...miraculously they do listen when it's about the bears...

9:00PM Lights out and we all snuggle in Isaac's bed for a bit and go through the usual procrastination routine "I want a drink of water", "I have to go potty", "tell Daddy to come kiss me goodnight". 

9:10PM Come downstairs and answer a few work-related emails, and then write this entry.  I can't believe it's an hour and twenty minutes later! 

10:45PM  Log off and go to sleep wondering what day I would have rather chosen for describing a "typical day" in the life of a physicist...

The Trouble with Parenting

April 9, 2005

I saw a very strange classified ad in a magazine this week:  it was under the heading "Psychiatry":

Phsychiatrist and Therapist ...Treatment for depression, anxiety, parenting, and psychosomatic symptoms.  Sliding scale.

At first I thought it was hilarious in a redundant sort of way-- parenting certainly has the potential to cause depression, anxiety, and psychosomatic symptoms, although hopefully not all at the same time.  Then I thought that really, the only cure for parenting is grandparenting, although that's probably not what the therapist is going to be pushing. 

But the bigger question that eventually crept into to my mind is this:  why is "parenting" in a list of illnesses that require treatment? 

When I was in the subway last month to visit the Chicago Academy of the Arts I saw a bilboard that I couldn't help but photograph, figuring that at some point I would rant about it to someone...it's at the left, and shows some guy in a suit trying to walk away from a child who is lying on the floor pulling his leg.  When I first saw that picture I felt guilty since I had left for the train that morning before my kids even woke up, and I couldn't help but remember times when Sonia or Isaac would pull on my leg to try and keep me from leaving them (of course the dramatics would always stop seconds after I left the room).  But if you look closely at this photo, you see that the kid isn't even looking at the dad who is walking away, he's looking straight ahead, as if his only purpose in grabbing dad's leg is to be a burden to him. 

What does it say about this culture that we are so often bombarded with images that portray our children as problems to solve or burdens we need to escape?  Obviously you don't see that sort of thing so much in Parenting, Child or Family Fun, but I don't feel so welcome in those pages either--there are all these projects being described that I don't have the time to put together, or vacations being presented that I can never imagine taking. 

Of course I don't need advertisements to tell me how to feel about being a parent, just like I don't need them to tell me how I should look, think, or vote.  But for some reason if there's a kid in the picture, I have to look. 

Crisis Management

April 5, 2005

In the spirit of full disclosure of what it's like to be a physicist, I figure I have to talk about what's been going on with MINOS lately.  Although in early March we made great advances figuring out how to run at "full speed", getting huge amounts of protons to our target, about two weeks ago we discovered a leak somewhere in the cooling lines that surround that same target, and we haven't been able to take the high intensity beam that we had just figured out how to deliver.  (The picture at the left shows Wes Smart and Virgil Bocean in December demonstrating the design of the target:  a long skinny thing with a can at one end that contains the ends of the cooling lines). 

What has evolved in the meantime has been a series of investigations into what happened to cause the leak in the first place, and whether or not the leak can be fixed without replacing the target.  You might wonder--how on earth can you look for a leak near some super-radioactive yardstick that is surrounded by tons of steel blocks?  Well, imagine you're looking for a leak--you look for where the water is.  How can you see water if you can't look at any of this directly?  It's like trying to figure out the shape of some object by shining light on it, but the problem is that all you can see is a screen a half a mile away from your flashlight:  if the light makes it through to the far away screen then you know there was no water to get in the way! Only in this case the "light" is a very thin beam of protons, and the screen is a charged particle detector at the very end of the decay pipe, which really is a half a mile away!  (The plot on the left shows the "light" hitting the middle of the screen as the beam scans across the target:  before the leak occured the two peaks were much higher than they are now)--thanks Sacha!).

The experiment is definitely in crisis mode, and people are studying different solutions to the problem--we have a spare target, the question is how to verify that this won't happen again and how best to replace the broken one.  When the news first broke we were all pretty shocked and people were walking around with very gloomy faces. 

If I take a step back for a second, the bigger picture is that MINOS will be taking data for several years, and this setback will hopfeully seem like small potatoes in the long run.  Taking even a bigger step away from the crisis, it's been rewarding to see how the detectors I helped design are being used in a way we never thought they would be used--I remember defending the design in a review where some of the reviewers were arguing that the detector at the end of the decay pipe could have just been some one-time use device like a big piece of polaroid film--that would have made these tests impossible! The picture on the left shows the real detector as it's being installed right after the decay pipe.  It may just look like a 1 square meter aluminum box with Texas longhorns on it, but that box is filled with an array of 49 radiation-hard "chambers" that can measure charged particles as they pass through the box. 

This is just another one of those cases where you have to "expect the unexpected". 

Winning the Lottery

April 1, 2005

Today I got the big news that Isaac won the lottery, or in other words he can go to the Fermilab summer camp when his school gets out.  This camp is a very popular program with not enough space for all applicants, so parents have to apply in the month of March for a spot and they hold a lottery to see who gets in on March 31.  Last year Isaac didn't get in to any of the sessions, so on April 1, 2004 I was searching for options in all the neighborhoods between where I live and the lab.  As it turns out, however, by April 1 the good all-day programs were full!  This year I wasn't taking any chances--by December I had reserved a spot for Isaac in a very popular all-day program just in case he didn't get in to the Fermilab program.   

Each time I look through the listings of camps for local park districts and community colleges I am struck by how many programs there are for kids who obviously have at least one parent who does not have to be at work from roughly 9 to 5 each day.  There are all these special programs that will run from 9:30 to 3 or better yet 10:30 to 2:30, or programs that will run for just a few weeks out of the entire summer.  There's maybe one or two programs with "extended hours", which I learned from last summer can mean nothing more than an exhausted teenager and a big room with a blaring television.  Are there so many more kids out there with only one parent working outside the house than with two parents working outside the house? 

One of the dangers of working at Fermilab (well, it's more like a double-edged sword) is that while you end up hanging out with all these interesting people from all over the world, you risk being pretty ignorant of your own neighborhood.  From reading the camp offerings around town, I would guess that Isaac is the only child in his class with two parents with full-time jobs outside the house.  Somehow I can't believe that's the case, though...

At any rate, the issue of "what is Isaac going to do this summer?" is off my list of worries, now I can go back to the remaining 99 things on the list...