(all articles are to be considered personal/professional in nature and do not reflect the opinions of the institutions described unless otherwise stated)
An Official Publication of the
Health Physics Society's Accelerator Section
Fourth Quarter 2014 /
- Two new particles found at the Large Hadron Collider (LHC): They have been named Xi_b’- and Xi_b*-, and are identical except for having a difference in spin. Both particles are composed of the same three quarks: Down, Strange, and Bottom. It’s fascinating that these new particles are composed of three quarks that are all of the same “color” (quantum chromodynamically speaking), as shown by the yellow circle in the below chart of the Standard Model (Symmetry, 11/19/2014).
- One hundred trillion of anything is bound to get attention. FermiLab is getting close to start producing that many neutrinos per second and shooting them 500 miles to the new NOvA detector in Minnesota. Construction of the NOvA Project’s detector, a state‑of‑the‑art device like no other, is now complete, and it use for studying neutrino morphing is to begin soon in earnest (Symmetry, 10/06/2014). Check out this cool video that’s all about the technical approach behind the NOvA detector: Detecting Neutrinos with the NOvA Detector
- Plasma wakefield
means of accelerating electrons Plasma wakefield
means of accelerating electrons: Scientisat at SLAC
National Accelerator Laboratory and the University of California, Los Angeles
(USLA), have found advanced ways using plasma wakefield
technology to push electrons to energies 400 to 500 times higher than
otherwise possible. This technology promises to yield more powerful
accelerators in smaller sizes that what we are used to seeing up to now. Who
knows? Plasma wakefield teconology
could make particle accelerators seemingly ubiquitous. (Symmetry,
11/05/2014) and Plasma
Wakefield Aceleration: How it Works.
may exist after all! In fact, they may help explain dark matter (SpaceDaily.com,
10/20/2014). Recent analysis of x‑ray energies from deep
space are producing hints that dark matter does indeed exist, indication of
which is observed via energy patterns shown by those same x-rays
that seem to be mirroring those predicted for axions,
a type of particle first suggested in 1977 by Dr. Helen Quinn of
SLAC and Dr. Roberto
Pecci of UCLA. Until recently, no proof that axions actually exist had been found. Now, proof may
be at hand. Stay tuned for further developments.
- Top Quark: why does it interact apparently more with Higgs Field than other quarks, especially with Top Quarks having rather similar rest energy-mass equivalence (173 GeV and 125 GeV, respectively (Symmetry, 10/15/2014).
- (From Quarks to Quasars, 12/17/2014) A new proposal interjects the Higgs Boson into better understanding charge‑parity violation as the basis for why there is more matter than antimatter in the Universe. Here’s how:
the above illustration, two protons collide at high energy, producing a Higgs
boson that instantly decays, producing two tau particles. The rest of the
energy from the collision sprays outward in two jets (pink cones). Measuring
the angle between these jets could reveal whether or not the Higgs is
involved in charge-parity (CP) violation, which could help us understand
matter and anti-matter. Image credit: SLAC National Accelerator Laboratory
- Interested in helping look for Higgs particles in the LHC data? All you have to do is go here to join the fun: Zooniverse Higgs Hunters.
but certainly not least, the science surprise of the year: Supersymetry (SUSY) evidence has not been found at LHC,
despite tailored efforts there to find it (Quanta, 1/22/2012).
Here’s a description of SUSY:
Supersymmetry proposes that every particle in the Standard
Model, shown at left, has a “superpartner” particle
still awaiting discovery (illustration: CERN & IESde
SAR). Source: Quanta Magazine.
the lack of proof at LHC mean that our faith in supersymmetry as the answer
for resolving the underlying difference between fermions and bosons, with the
possible difference being the driver behind the ongoing expansion of the
universe (i.e., dark energy), is
wrong? Since the date of this article in Quanta two years ago, the lack of
proof continues; to date, none has emerged from any data anywhere. Let’s keep
following this potential development as more information emerges, especially
as LHC renews the search at higher energy levels in 2015.
summary, all of the above point to an exciting year in 2015!
PS. One more
little reminder that the HPS Mid‑Year Meeting is coming up soon. It
will feature a new, more versatile format that previous mid-year meetings.
Please consider attending! The meeting will be held in beautiful Norfolk, VA,
from February 1stthrough the 4th of 2015. You can access the meeting
website at http://hps.org/meetings/meeting41.html for
Linnea Wahl, The Secretary/Treasurer:
FROM THE CORRESPONDENTS
From Scott Schwahn, Spallation Neutron Source
Spallation Neutron Source (SNS) has experienced unplanned and previously
unanticipated maintenance challenges since summer 2014. At the center of neutron
production is a stainless steel target inside which circulates approximately
20 tons of liquid mercury. The nose of the target is struck by an
approximately 1 GeV, ~1 MW (average) proton beam
operating at 60 Hz. It is expected that the target will be damaged over time
and it has to be replaced regularly. Internal cavitation damage is
theorized to occur as approximately the cube of proton beam power. Up until
recently, the target lifetime has typically been 6 months or
more. With each target costing more than $1 million USD, quite a bit of
research has gone into finding ways to extend the life of the targets.
Large view of the front end cage, normally a Radioactive Material Area during maintenance. Usually posted as a Radiation Area during operations.
far as radiological safety goes, these problems presented us with numerous
challenges, although there was never any danger of contamination beyond the
immediate area of the leak. The front end of the accelerator is normally
defined by a relatively small “Radioactive Material Area (RMA)” – in the US
Department of Energy scheme, that’s an area where any materials present have
to be assumed to be radioactive unless they were personally brought in and
carried out upon leaving. In fact, there is not normally a posted RMA outside
of the access-controlled tunnel (the first 10 meters or so of the accelerator
is outside of the tunnel). However, nearly every component of the beamline –
every sensor, vacuum connection, beam pipe, magnet, radiofrequency cavity
– had to be individually disconnected, labeled, evaluated, and treated for
water and air intrusion. (This had never been performed or anticipated to be
performed since the accelerator was first constructed, and included many
one-of-a-kind items that could not be replaced!)
Accelerator section that had to be completely dismantled to address the water leak.
Typical size of a "staging RMA". During the front-end activities, the area was expanded by perhaps a factor of 6.
Everyone was quite pleased that in the end, not only
were there no radiological safety violations of procedure, the entire
accelerator was put back together properly and functioned properly. I could
not begin to adequately describe the other work that was done to prevent
damage to components and to dry out items that should have never seen water,
but could not be taken apart. Of interest, there were items such as
elastomeric washers that trapped water but could not experience significant
heat or they would be damaged; and could not dry out under vacuum or the
water would freeze. An interesting problem, solved by an external glycol bath
held just a few degrees above 100 degrees C.