Physics
Stanford Linear Accelerator Center
High-energy physics researchers and administrators meet over NeXT technology
Reproduced with permission from NeXT
Computer, Inc.
A Reference
Guide to NeXT in Higher Education, Fall 1992
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1992 NeXT Computer, Inc
At Stanford Linear Accelerator Center (SLAC), physicists
and administrators alike use NeXT technology in all aspects
of their work, from developing computing tools for data
analysis to organizing an annual two-week summer institute.
The primary interest of Staff Physicist Paul Kunz, a NeXT
computer user since 1989, is developing computer
applications so scientists can visualize their manipulation
of data in a highly interactive manner. For example, with
Reason and HippoDraw-applications developed by Kunz and his
colleagues-scientists can create analysis chains with a
mouse rather than by writing computer code. Scientists
select an input (for example, a file containing data about
physics events) and set up the necessary analysis, which
could take minutes or hours depending on the size of the
data sample. The output of the analysis is a large table of
numbers, displayed as histograms, scatter plots, or graphs.
Because these plots are produced almost instantly, users
see the results of their work immediately.
"We chose the NeXT platform because of the NeXTSTEP
development environment, particularly Interface Builder,
which enables us to build applications quickly," says Kunz.
"Scientific workstations today have a minimum of 10 MIPS, 8
MB memory, and a 1-megapixel display. This kind of power is
relatively new in our environment. However, the so-called
interactive interfaces we usually see are really
accelerated batch interfaces; we type something, then wait
for results. NeXTSTEP's graphical interface and development
environment let us create truly interactive tools. As we
move a slider to change a variable, we see our plots change
immediately."
Using Reason and HippoDraw, Kunz and his colleagues have
already analyzed many data sets containing thousands of
physics events. "It used to be the case that working with a
computer involved a trade-off," Kunz says. "We'd have an
idea of what we wanted to do, but completing the program
for it would often take weeks or months. The time it takes
to develop a program with NeXTSTEP is faster by a factor of
at least five. When a program is this much faster to
develop, researchers can drive to work in the morning,
thinking, 'What new thing should I create today?' With the
previous generation of platforms, they drove to work
thinking, 'I wish I could finish today what I started last
week.' That's a big difference in approach and
productivity."
In designing Reason, Kunz was careful to separate general
data analysis functions from functions specific to physics.
The application provides a palette of objects that perform
operations such as input, output, and looping. HippoDraw,
meanwhile, handles the plotting of histograms.
Physics-specific objects are organized on a user palette.
Users can also write their own objects to perform any
number of functions and include these on the user palette.
As a result, the application can be customized to perform
tasks applicable not only to physics but to any field
requiring statistical analysis.
Kunz says SLAC physicists have also developed a NeXT
computer application that is a front-end interface to the
Minuit kernel, the standard minimization program. Given a
set of points that should match a known function-for
example, a Gaussian distribution-the program plots the
curve that best describes the function and calculates the
function's parameters.
There are three advantages to the NeXT version of the
Minuit program, according to Kunz. "First, it's really fast
to do a fit. Second, it uses an existing program that many
scientists regard as a trusted friend. Third, the program
shows the curve that would result when taking into account
the error on any parameter. For example, if the error is +
1 percent, the user can see the resulting curve simply
moving the slider on a scale from -1 to +1."
Staff Physicist Bill Atwood is using the NeXT machine to
model particle physics experiments. "Particle physics
research used to be at the cutting edge of computer
technology," he says. "Today, however, we're years behind
other sciences: most of our code for particle research is
written in FORTRAN 77. While on-line data acquisition
techniques and end-user data analysis tools have improved,
the core computing environment is outdated. One of my
projects is to take the core FORTRAN procedural language
codes used to model particle physics experiments and make
them current in today's technology. For us, that means
using NeXT."
During a particle physics experiment, particles are shot
through accelerators to collide with one other or with
particles in a target. The collision occurs in a detector
that is constructed by layering tubes of different size,
material, and physical properties. The particles that
result from the collision can be recognized by their
trajectories and by the layer of the detector in which the
ionization trails are recorded.
Gismo, a program which was co-author by Atwood and other
scientists from the United States and Europe, lets
physicists model a detector that specifies the radii of its
layers, materials, and magnetization, and then simulates
particle collisions. The application registers as many as
20,000 points from a typical collision, then uses pattern
recognition algorithms to plot straight and curved lines
showing the trajectory of each particle. The resulting
graph is a dramatic display with different colors
representing the various particles and their energies.
"Until recently," says Atwood, "detectors were designed by
people who guessed on the optimal detector design based on
previous experience. Gismo lets us tell ahead of time what
benefits we'll derive from a particular design."
At SLAC, the administrative staff also uses NeXT computers.
According to Steve Williams, assistant director of the
research division, the display on his NeXT computer on a
typical day might contain windows for a terminal session
with the mainframe, a Lotus Improv spreadsheet containing
lists of people in the SLAC user organization, a FrameMaker
document for creating form letters for job offers, an
organizational chart created with Diagram!, a to-do list
created in WriteNow, and a calendar program.
SLAC Administrator Jane Hawthorne uses a NeXT machine to
coordinate annual summer institute. She uses FrameMaker to
manage a database of summer institute participants,
correspond with students in the postdoctoral research
program; and maintain a list of caterers, entertainers, and
other vendors she uses in coordinating the institute. Says
Hawthorne, "The NeXT gives me the ability to do three or
four things or more at once much more effectively than
other computers I've used."
For more information, please contact:
Paul Kunz
Staff Physicist
Stanford Linear Accelerator Center
Stanford University
Stanford, CA 94305
(415) 926-2884
pfkeb@kaon.slac.stanford.edu