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On September 6th, the solenoid from the CLEO detector was removed from the area known as L-Zero at Wilson Synchrotron Laboratory, the former interaction point of electron and positron colliding beams. The migration of this 26-ton superconducting magnet marks the last major component to be removed from the detector as the lab prepares for its next major upgrade, CHESS-U. After months of disassembly of the structural steel, iron rings, calorimeter and interleaved muon chambers, the CLEO solenoid will soon be transported to its new home at Jefferson Lab in Virginia, where it will come out of retirement for a whole new set of experiments.
The 26-ton solenoid being removed from L-Zero.
For nearly thirty years CLEO operated as a high-energy physics detector, from 1979 to 2008, recording the particles produced in electron-positron collisions at the Cornell Electron-positron Storage Ring (CESR). CLEO carried out a broad physics program of studying the production and decay of bottom and charm quarks, as well as tau leptons, and to search for new phenomena beyond the Standard Model of particle physics. To meet the evolving needs of this wide-ranging physics program, CLEO underwent five major upgrades, each incorporating new technologies in particle detection and identification, as well as implementing advances in computing and software.
March 3rd, 2008 marked the last run where CLEO took in data. The high-energy physics team had previously branched out to studying high energy proton-proton collisions using the Compact Muon Solenoid (CMS) at the Large Hadron Collider (LHC) and muon decay with the g-2 experiment at Fermilab . Meanwhile, the partial skeleton of the CLEO detector remained at Wilson Lab, encircling the CESR beam pipe, where electron and positron bunches no longer collided, but continued to travel smoothly through its center.
With the removal of CLEO as the first step in CHESS-U, the storage ring will soon be able to operate with a single beam of positrons instead of counter-rotating electron and positron beams, eliminating many of the performance limitations associated with the present two-beam operation. This will also enable all CHESS beam lines to be aligned to a single beam orbit, enhancing the x-ray beam quality for research in physics, chemistry, biology, and environmental and materials sciences.
Jeff Mangus, left, and Dana Richter, discuss the best method to remove the solenoid.
As the pieces of CLEO were carefully set in place decades ago, they also had to be carefully extracted. During the removal of the calorimeter, the engineers had to raise the remaining structure of CLEO, weighing over 180 tons, to ensure that the calorimeter would not graze the steel floor as it slid horizontally from inside the solenoid coil. Existing jacks that had not been put to use in over eighteen years were turned on to elevate the detector a mere two inches. These jacks were able to give the team the amount of space needed to pull the calorimeter along the steel beam placed inside. Inch by inch, the crew manually removed the cesium iodide calorimeter that was pressure-fitted onto the same large mandrel with which it was installed in 1988.
The team at Wilson Lab is now focusing on the reassembly and commissioning of the storage ring, where users will start experiments on October 26th. CHESS welcomes over 1,200 scientists and scientists-in-training annually to collect data that comprises all or part of their research programs at the facility. It is supported by grants from the Division of Materials Research of the National Science Foundation.
Submitted by: Rick Ryan, CHESS, Cornell University