Components for CERN’s Large Hadron Collider are moving into the production stage.

by Mike Perricone

From teleconferencing to kicking the tires, communication and contact are the critical issues as Fermilab’s US/CMS Project swings into production mode.

"Things are cooking," said the project’s technical director, Dan Green.

The project is building components for the Compact Muon Solenoid detector, a major element of the Large Hadron Collider being constructed at CERN, the European particle physics laboratory in Geneva, Switzerland.

When the LHC begins operating, projected to be sometime around 2005, it will shift the frontier of high-energy physics away from Fermilab’s Tevatron. But by making integral contributions to the LHC, Fermilab maintains its stake in the future of accelerator and detector development. Scientists, engineers and technicians at Fermilab establish their status as "co-pioneers" for the new frontier, and build the Lab’s credentials for the opportunity to build a future machine for moving beyond the LHC’s capabilities.

But US/CMS efforts are rooted in the present, aimed at creating what Green called "the best detector we can deliver for the money." The Fermilab projects for the CMS detector focus on the hadron calorimeter, which measures the angle and intensity of energy produced in a particle collision; and the muon cathode strip chambers, which measure the momenta of the muons (heavy cousins of the electron) in CMS interactions.

Several members of the Lab’s CMS Project recently returned from a regular quarterly meeting of the entire collaboration at CERN. The collaboration also holds weekly teleconferences on technical progress, but Green emphasized that the weeklong meetings at CERN are as valuable as they are grueling.

"You have to learn how to attack problems in an international collaboration," he said. "Our view is that if problems arise, they are common problems—not just the problem of one country, or the problem of a subsystem where one country bears most of the responsibility. If you adopt that strategy, then you can imagine building the best detector with the collective money we have.

"We do have a common language, the language of physics. If we keep the discussion on the level of physics, we can often come to an agreement."

Another common language: kicking the tires, which is what Jim Freeman did at CERN during the quarterly meeting.

"I went over and kicked the tires on the motion table, which is now installed over there," said Freeman, referring to the 40-ton platform fabricated by the Industrial Maintenance Welding and Machining Company on Chicago’s South Side.

The motion table was undergoing a test, in which it was loaded with 170 tons of steel blocks. "It only deformed by a few millimeters, which was very good," Freeman said.

The motion table, which can move both horizontally and vertically, will hold a pair of 30-ton wedge-shaped prototypes of the hadron calorimeter detector when CERN runs beam tests this summer. The motion table will move the detector prototypes around in the beam, simulating multiple angles of collisions. But first, the prototypes have to be put on the table.

"We can put the first one on using lifting straps, which are the nylon ropes that you hang from a crane hook," Freeman explained. "But with the second one, we can’t use the straps. They fit tightly together. The first one has clearance, so we can use the straps to lower it down, and then we can clear the straps out of way. But the straps would be pinched between the two if we lowered the second one that way. We have a consulting engineering company in the Fermilab area that’s designing a lifting fixture. But if it’s not done in time, we’ll have to jury-rig something at CERN."

Freeman said CMS activity is taking place "everywhere" at Fermilab. Some examples:

Down the hall from Freeman’s and Green’s offices on the sixth floor of Wilson Hall, a group of four engineers working full time on the hadron calorimeter has completed the calorimeter design and is moving on to the task of designing the tooling, including the cradle that will be used in constructing each half of the calorimeter—with each half weighing about 500 tons.

On the 14th floor, Ray Yarema’s electrical engineering group is designing ASIC (Application Specific Integrated Circuits) chips. "They have to be right from the beginning," Freeman said. "They’re not like circuit boards that can be touched up and fixed. There’s no way to modify these and correct errors."

In Lab 5, 11 technicians (approaching the planned full strength of 13) are working on the scintillators for the actual detector wedges, not just for the prototype wedges.

Components for the summer test beam run are also being produced at universities ranging from two in the South (Florida State and Mississippi) to two in the East (Maryland and Rochester) to five in the Midwest (Minnesota, Purdue, Iowa, University of Illinois-Chicago and Notre Dame).

"In principle," Freeman said, "all the components will be shipped to Fermilab around the first of April. We’ll spend a month integrating them, making sure everything works together, running tests, ironing out bugs. Then around the first of May, we’ll pack it all up and ship it to CERN."

Late in May, a team led by Fermilab will go to CERN to install the readout system, cabling and electronics onto the detector prototype, with test beam activities scheduled for June.

"Things always get hectic right before test beams, but that’s also a good thing," Freeman said. "It brings everything together. Everybody knows there’s a deadline, and that serves as motivation. It focuses your attention."

After his trip to CERN, Freeman swung by a factory in northern Spain where Spanish collaborators are building detector wedges. The second wedge is assembled and mounted on a giant milling machine (the bed is 50 feet long by 15 feet wide) built in the Czech Republic. Each half of the calorimeter (called a half-barrel) consists of 18 wedges, for a total of 36. The first 18 are scheduled for delivery to CERN in May 2000.

"That’s only 13 months from now, and it’s a tight schedule to keep," Freeman said.

Maintaining contact is critical for quality control, and a Fermilab engineer, Igor Churin, will travel to Spain in April to supervise stress testing of the prototype detector components. Then he will supervise a full survey using photogrammetry, in which digital images of several selected points are used to create a three-dimensional reconstruction of the wedge.

"We purchased a photogrammetry system for our quality control," Green explained. "After the prototype, the factory workers themselves can do the photogrammetry, and then send the file for us to check for quality."

Last month’s review by the Department of Energy gave the overall project high marks for quality. US/CMS was told it could expect to expand the scope of its efforts by about $4 million at the time of the next full baseline review in February 2000.

"We’ll get proposals, set priorities and then get together with the full experiment," Green said. "I believe very strongly that if we’re going to have the best detector, we must fully consult with all our colleagues. We’re not going to change the scoping in some way defined only by the U.S."

One obstacle to full consultation is the diplomatic strain between the U.S. and India over India’s testing of nuclear weapons. Sanctions by the U.S. State Department prevent US/CMS members from visiting India’s Tata Institute, where some intricate plastic detector components are being fabricated. An engineering review of the work will be conducted at CERN, but Green, who is responsible for coordinating all the international efforts, would like to see what’s going on for himself.

"I hope the issue can be settled," he said. "I really want to go over there and see the factory in operation."

Not to mention kicking the tires.