John H. Malmberg

John Holmes Malmberg (July 5, 1927 – November 1, 1992) was an American plasma

Neutral plasmas are notoriously difficult to confine. In contrast, Malmberg and collaborators predicted and demonstrated experimentally^[3][4][11] that plasmas with a single sign of charge, such as pure electron or pure ion plasmas, can be confined for long periods (e.g., hours). This was accomplished using an arrangement of electric and magnetic fields similar to that of a Penning trap, but optimized to confine single-component plasmas. In recognition of Malmberg’s contributions to the development of these devices, they are now referred to as Penning–Malmberg traps.

Malmberg and collaborators, realized that

In the late 1980s, pure positron (i.e., antielectron) plasmas were created using the Penning–Malmberg trap technology.^[20] This, and advances in confining low-energy antiprotons,^[21] led to the creation of low-energy antihydrogen a decade later.^[22][23] These and subsequent developments^[24][25] have spawned a wealth of research with low-energy antimatter.^[26] This includes ever more precise studies of antihydrogen and comparison with the properties of hydrogen^[27] and formation of the di-positronium molecule (Ps${\displaystyle _{2}}$, ${\displaystyle e^{+}e^{-}e^{+}e^{-}}$)^[28] predicted by J. A. Wheeler in 1946.^[29] The Penning–Malmberg trap technology is now being used to create a new generation of high-quality positroniumatom (${\displaystyle e^{+}e^{-}}$) beams for atomic physics studies.^[30][31]

In the broader view, Malmberg’s seminal studies with trapped single-component and non-neutral plasmas have stimulated vibrant sub-fields of plasma physics with surprisingly broad impacts in the wider world of physics.

Honors and awards

In 1985, Malmberg received the James Clerk Maxwell Prize for Plasma Physics from the American Physical Society for "his outstanding experimental studies which expanded our understanding of wave-particle interactions in neutral plasmas and increased our confidence in plasma theory; and for his pioneering studies of the confinement and transport of pure electron plasmas".^[5]

And in 1991, he was co-awarded the

In 1993, the UCSD physics department established the John Holmes Malmberg Prize in his honor. It is awarded annually to an outstanding undergraduate physics major with interests in experimental physics.[32]

References