Inside the ALS

America’s brightest source of light 1 Electron Source 2 Linear Accelerator 3 Booster Ring Synchrotron Radiation At every curve in their path, the H ranging from the ultraviolet through The electron source is a button-sized piece of The electrons travel though a linear The electrons race around a booster ring F tungsten (the same material that is in the accelerator, a copper structure shaped such more than 1 million times, forced into a electrons emit light (not just visible V light, but everything from filament of an incandescent light bulb) that that radio-frequency (rf) waves travel through near-circular path by magnets. They get a radiation lower-energy (“soft”) x-rays is not a fan releases electrons when heated to 1000 °C. it at the same speed as the electrons. This boost in energy on each turn from an radio-frequency waves to dipole laser, a medical x-ray machine, or even A screen near the electron source is given a way, the electrons are accelerated by the rf accelerating rf cavity, but even so, they x-rays) forward like a car headlight. Electrons strong, short-lived, positive charge 125 waves as they travel through the structure, can’t go faster than the speed of light. So S million times each second, and this positive like a surfer riding a wave. while the booster ring increases the curving through the the sun. It is a beam of electrons, Electromagnetic wave is traveling, charge pulls the negatively charged electrons away pushing particles along with it. energy of the electrons by almost 40 storage ring’s dozens of dipole bend magnets emit accelerated to almost the speed of from the electron source in bunches of billions of + times, it mostly goes into increasing their N electrons each. mass, not their speed. Once the electrons fanlike beams of photons (particles of light). Between these curves are straight sections light by a particle accelerator, called a - reach their target energy, they are where multi-magnet arrays, called insertion devices, wiggle the Positively charged particles ( ) close to transferred to the main storage ring, the crest of the EM wave experience where they circulate for hours. electrons back and forth. The light from each wiggle overlaps and forms a synchrotron, at the Advanced Light the most force forward; those closer to the center experience less of a force. narrow beam 100 million times brighter than conventional x-ray sources. The result is that the particles tend to Source (ALS). Inside the ALS tells how bunch closer together. the electrons start out, speed up, gain 4 Storage Ring Electrons zip around the main storage ring 5 Rf Cavities energy, and produce exceptionally 1.5 million times a second, producing light Every photon that an electron every time a magnet changes their direction. emits carries away some of bright light. This light fuels scientific The electrons travel in a vacuum chamber, the energy of the electron. where the number of molecules per unit This energy is replenished experiments from physics to forensics. volume is comparable to the surface of the each time the electrons moon, so there are almost no collisions. In travel through the two rf regular air, the electrons would on average cavities in the storage ring ELECTROMAGNETIC SPECTRUM make it about 1 meter before hitting a (like the one in the booster). The electromagnetic (EM) spectrum covers a wide range of molecule and being lost. 2 wavelengths and photon energies. EM waves used to “see” 1 an object must have a wavelength about the same size as or smaller than the object. Longer-wavelength radio waves can 6 Dipole Bend 7Quadrupole 8 Insertion Devices only resolve large structures. Visible light allows us to see 9 8 3 Insertion devices, placed in the straight sections Magnets Magnets between the bend magnets, use a series of very whole cells or bacteria. But to look at smaller structures, To keep the electrons on their curved path, dipole Quadrupole magnets focus the electron beam, short permanent magnets to wiggle the electrons like viruses or molecules, we need shorter wavelengths. The bend magnets are used. They are essentially large, similar to the way lenses focus light beams. We from side to side. This results in a much smaller but brighter fan of light. ALS is an extremely bright source of shorter-wavelength horseshoe-shaped magnets. The vertical magnetic actually calculate the size of the electron beam field they produce deflects the electron beam using the same mathematical formalism used for energy — primarily x-rays — that is used for many different 4 7 6 horizontally. The main storage ring at the ALS has light optics. types of research. 36 dipoles, each bending the beam by 10 degrees, 5 resulting in a 10-degree fan of light.

1 yd 1 ft 1cm1mm 1μm1nm 1Å 1pm 3 2 1 -1 -2 -3 -4 -5 -6 -7 -8 -9 -10 -11 -12 Wavelength 10 10 10 1 10 10 10 10 10 10 10 10 10 10 10 10 (in meters)

Soccer Field House Baseball Point of a Needle Cell Bacteria Virus Protein Water Molecule longer shorter

Size of a wavelength 9

Common name Radio Waves Infrared Visible Ultraviolet “Hard” X-Rays 9 of wave

Microwaves “Soft” X-Rays Gamma Rays

Cell Phone

GPS Advanced Light Source Sources WiFi

Baggage People Screen

TV Satellite AM Radio Microwave X-Ray Radioactive Oven Radar Remote Light Bulb Machine Elements Frequency (waves per second) 10 6 10 7 10 8 10 9 10 10 10 11 10 12 10 13 10 14 10 15 10 16 10 17 10 18 10 19 10 20 9 Beamlines and Endstations 1 MHz1GHz1THz1PHz1EHz1ZHz lower higher Beamline mirrors steer and focus a thin beam of photons down meters of vacuum pipe Energy of one photon -9 -8 -7 -6 -5 -4 -3 -2 -1 1 2 3 4 5 6 (electron volts) 10 10 10 10 10 10 10 10 10 110 10 10 10 10 10 from the storage ring to the target: a sample of interest in an experimental chamber (endstation). Some experiments use all the available photons, but the storage ring 20-ALS-1067 ENERGY SCIENCES produces so many photons, scientists can afford to be choosy about which photons they Despite conventional wisdom that reactions involving oxygen will reduce a use. Often they select only photons with a certain wavelength (“color”). battery’s rechargeability and safety, experiments performed at the ALS showed Researchers make observations by using the photons to produce small changes in their that some oxygen reactions are both beneficial and reversible. The results open up sample, and a variety of instruments record the results. Computers help convert the Science at the ALS new ways to explore how to pack more energy into batteries with electrodes made instruments’ readings into images, graphs, or even 3D models, making new information out of low-cost, common materials. available for advancing science and technology. CHEMICAL SCIENCES MATERIALS SCIENCES APPLIED SCIENCES Magnesium/sulfur batteries hold promise as a safer, more compact alternative to To store more information in less space while conserving power, scientists are Solar cells printed on plastic film using a photovoltaic “ink” are a potential source of lithium batteries, but they have suffered from extremely limited recharging studying materials that contain tiny, swirling magnetic and electric structures that inexpensive renewable energy, but some efficiency is lost in the transition from lab to capabilities. To learn more about why, researchers used the ALS to investigate the could be used to encode binary data. At the ALS, researchers confirmed the binary factory. To understand why, researchers put a factory-type solar-cell printer inside an batteries’ chemistry as they’re charged and discharged, identifying the limiting steps nature of such swirls in a material that, crucially, allows for them to be controlled ALS beamline, allowing them to study changes in the ink’s molecular structure and and pointing the way to a solution. using an external electric field. chemistry as it dries. EARTH AND ENVIRONMENTAL SCIENCES PHYSICAL SCIENCES BIOLOGICAL SCIENCES Researchers used the ALS to study comet dust particles, which are “forensic” Researchers at the ALS showed that computers can learn to predict noisy Amgen Inc. identified a promising anticancer drug that targets tumors caused by material samples preserved from the birth of the solar system. Their analysis of the fluctuations in the size of beams generated by synchrotron light sources and mutations in a type of protein that signals cells to divide and proliferate. Crucial particles’ structure and composition, at unprecedented spatial scales and sensitivity, correct them before they occur. This "machine learning" approach solves a atomic-level information about how the prospective drug molecule interacts with the identified certain complex mineral grains as likely to be the original “bricks and decades-old noise problem and will allow researchers to fully exploit the smaller cell-signaling protein was revealed using light from the ALS. mortar” of the solar system. beams made possible by recent advances in light source technology.

21-ALS-1080