A "splash event" in the LHCb detector, recorded during an injection test in 2009 (Image: LHCb)
With the Large Hadron Collider
(LHC) due to start up again at the end of this month, the team in the
LHC Control Centre are busy testing the systems that deliver the beams.
At CERN, a series of accelerators
boosts protons or ions to successively higher energies until they are
injected into the LHC. The LHC then further accelerates the particles
before delivering collisions to the four detectors ALICE, ATLAS, CMS and LHCb. The penultimate accelerator in the chain is the Super Proton Synchrotron (SPS), a machine nearly 7 kilometres in circumference, which receives particles from the Proton Synchrotron at 26 GeV, and boosts them to the 450 GeV needed for injection to the LHC.
Now, the LHC control team is testing the injection systems to ensure
that the upcoming startup of the accelerator runs as smoothly as
possible. Though particles will be injected into parts of the LHC this
weekend, there will be no fully circulating beams until the planned
startup at the end of this month.
"We will do two tests," says Ronaldus Suykerbuyk of the LHC operation
team. "Beam 1 will pass through the ALICE detector up to point 3, where
we will dump the beam on a collimator, and for Beam 2 we will go
through the LHCb detector up to the beam dump at point 6." A screen
placed in the beam pipe will register a successful pass as a bright dot.
The team will also record other parameters, including the timings of
the injection kickers – fast pulsing dipole magnets that "kick" the beam
into the accelerator – and the beam trajectory in the injection lines
and LHC beam pipe. Beams
will not circulate all the way around the LHC, but rather reach point 3
and point 6 during the tests (Image: Leonard Rimensberger/CERN)
"This test really is a massive debugging exercise," says Mike Lamont,
head of the operations team. "We've already pre-tested all the control
systems without beam. If the beam goes around we’ll be happy!"
The ALICE and LHCb experiments are preparing their detectors to
receive the pulses of particles. "ALICE will receive muons originating
from the SPS beam dump," says ALICE physicist Despina Hatzifotiadou,
"They will be used for trigger timing studies and to align the muon
spectrometer".
LHCb will also be taking data. "These tests create an excellent
opportunity for us to commission the LHCb detector and data-acquisition
system. The collected data are also invaluable for detector studies and
alignment purposes, that is, determining the relative geometrical
locations of the different sub-detectors with respect to each other,"
says Patrick Robbe of LHCb. "It's exciting because the tests show that
we are getting closer and closer to the restart!"
But there is still much work to do before first circulating beams,
says Suykerbuyk. "We have to finish all the powering tests and magnet
training as well as test all the other hardware and beam-diagnostic
systems." It's going to be a busy few weeks for all concerned.
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