SciBooNE or: How I learned to stop worrying and love the MRD

After many months of cajoling, I feel that I should write a blog entry on what I have been doing whilst living out here in the USA other than enjoying their fine beers, moderately sized meals and small economic vehicles.

I suppose I should first explain how I came to work on SciBooNE in the first place. In January 2006 I joined the T2K group my supervisor, Morgan Wascko, a new lecturer joining the group. As it turned out Morgan was also co-spokesperson on the SciBooNE experiment which at that stage was a proposed experiment to be built out at Fermilab to measure sub-GeV neutrino cross-sections of interest to T2K. After some discussion it was decided that this would be a good opportunity for me to get some hardware experience by going out to Fermilab and helping in the construction of one particular element of the detector, namely the Muon Range Detector (MRD).

The MRD is an iron-scintillator sandwich detector consisting of 13 alternating horizontal and vertical layers of counters separated by 5cm of iron. The total depth of iron in the detector is 60cm which corresponds to stopping a 900MeV muon. The purpose of the MRD is to measure the energies of muons produced in neutrino interactions, for example charged current quasi-elastic (CCQE), where a muon and a proton (muon neutrino) or neutron (muon anti-neutrino) are produced. By measuring the muon energy the neutrino energy can be reconstructed.

In May 2006 I visited Fermilab for 1 month to construct and test the prototype counter design for the MRD. By June the design had been approved and mass counter assembly could begin.
I returned to Fermilab in July this time to assist in the full counter assembly which got underway at the beginning of that month. With 362 counters to be made and 3 days needed for each counter to be produced this would be the largest single job for the MRD construction. The final counters were finished in December just in time to begin the detector assembly in January. At this stage it was decided that I should move to the States to help complete the detector construction and to see it through the beginnings of its data run.

The MRD is a unique detector in the fact that it is almost completely constructed from previously used materials. The scintillator panels (20cm x 155cm x 0.6cm) were taken from an earlier Fermilab experiment whilst 5 different photomultiplier tube (PMT) flavours are used to readout these counters. The iron having enjoyed a number of years outside in the elements had to be cleaned before it was ready to be used. Even some of the cables, both high voltage and signal, had been previously used. When it came to inspect these cables, in storage in a disused detector hall, they were found in a mess, you could say a ratsnest, not so much because the cables were tangled but rather a ratsnest! As 2 grad-students went about untangling the cables two 'rats' (though they could have been large mice) emerged from their makeshift home. Needless to say this added considerable time to the cable inpections as every inch had to be checked for damage and a number were rejected having been partially chewed!
The PMTs have a range of ages, from relatively new tubes used in the KTeV and NuTeV experiments, to RCA tubes that date to the early 70's and no doubt have been used in a number of different experiments over the years. As you can imagine this produces particular problems when it comes to understanding your detector efficiencies. It is a credit to all those involved in the construction that when the detector was switched on in May 2007 only 3 of the 362 channels were found to be dead, well below our expectations.

In January the detector construction got underway in Lab F on the Fermilab site. At this stage SciBooNE, a supposedly small experiment, was starting to sprawl. Office spaces could be found in Wilson Hall, the CDF trailer and the main CDF building. As for the detector construction, the CDF pit was devoted to SciBar and the EC whilst the MRD had spaces at Lab F and Lab 6 not to mention cable repairs taking place at the D0 hall and the civil construction of the SciBooNE hall in the Booster neutrino beamline. SciBooNE was maturing fast and with the aggressive schedule put forward the hope was to see a completed detector by early June in time to commission before the proposed shutdown in August.

The MRD construction proved to be a challenge. Initially the first few planes proved trivial to construct. However as more and more planes were added to the frame so the space between planes diminished. By the time the detector was completed the space between planes was 30cm (the depth of a fermilab standard issue hardhat!) Unfortunately by this stage the american portions had got the better of myself and Nakaji (nickname: 'The Blackhole') and so it was to the smallest of our collaborators, Kendall Mahn (5' 2") to complete the work. We looked on eating doughnuts (raspberry cream I believe).

The detector construction was completed in March and was partially cabled allowing us to test the DAQ system with one week of cosmic data. The move date was set for 23rd April, and so it was apt that "Once more into the breech" was mentioned more than once that day as a 360 ton crane lowered, i've been told i'm not allowed to say dropped, the MRD into place. SciBar and the EC were lowered 2 days later.

At this stage a number of tasks in the detector hall had to be undertaken and it was hoped that the MRD cabling would begin around the 25th May and be completed by early June. However with NuInt, a neutrino interactions conference, to be held at Fermilab from 30th May until 3rd June it was with a last gasp of energy that we pushed to complete the cabling early so as to show beam events at the conference. As you can see from Morgans post we succeeded in doing so but I think it is an astonishing feat that we completed the cabling of the detector on the 24th May, 1 day before we were meant to start!

I hope this has given you a little insight into SciBooNE and the MRD, I personally feel that it is astonishing that such detectors, both SciBar/EC and the MRD, can be constructed in such a short space of time. In a little more than a year a detector went from merely a blueprint with a counter design that had yet to be confirmed as suitable, to a detector taking data. SciBars timeline is equally incredible given that it was shipped in from Japan and had to be reconstructed with a new support frame and DAQ system. It has been a great experience to work in such a dynamic collaboration, I hope this continues. All SciBooNE collaborators must be congratulated for all their hard work.

P.S. I am in the process of making a website where I will be posting photos of the MRD construction among other things T2K/SciBooNE related. I will post a link in due course.