Professor Andrew Lang: Pioneer of X-ray diffraction physics

Distinguished for his pioneering studies in X-ray diffraction physics, especially for his development of the technique of X-ray topography, Andrew Lang will be greatly missed by many researchers for his detailed knowledge of crystal physics.

Crystals are regular three-dimensional arrays of atoms, packed together in evenly spaced unit cells. Departures from regularity, or crystal defects, significantly modify the useful physical properties of industrial materials, such as their strength, colour and electrical conductivity. Lang developed topographic techniques to image certain imperfections in crystals, such as dislocations, stacking faults, growth-sector boundaries and ferromagnetic domains. One such technique, the projection topograph, displays the internal imperfections throughout a crystal and this is often called the "Lang method". For the past 50 years, Lang's methods have been widely used in the non-destructive assessment of crystals for the electronics, diamond and other industries.

A diffraction pattern may be produced by visible light passing through a fine silk cloth or by X-rays passing through the regular lattice of atoms in a crystal. When a beam of X-rays enters a crystal at particular angles of incidence, it is possible for the planes of atoms to reflect the X-rays ( according to Bragg's law). The waves in the transmitted beam and in the reflected beam may interfere to produce another wave: in effect a moiré pattern.

Lang studied many types of X-ray diffraction phenomena, including variations from Bragg's law, X-ray moiré patterns and other types of fringes. His most important discovery in this category (with Norio Kato in 1959) was that of interference fringes in wedge-shaped perfect crystals, in which the fringe spacing gave a precise measure of the scattering power (or absolute structure amplitude) from a unit cell. Using synchrotron X-radiation, Lang and his research team were also able to measure and to map the small variations in the separation of carbon atoms across a 5mm synthetic diamond with an accuracy better than one part per million.

Lang also made significant discoveries using other techniques, especially electron microscopy and cathodoluminescence. For the latter, high-energy electrons are directed on to a specimen surface and the visible luminescence is recorded. Using these techniques separately and in combination with X-ray topography, he studied a wide range of crystalline materials, including metals, semiconductors, quartz and diamond. His first published paper (1947) was on the crystal structure of a potassium soap.

His work exhibited sustained innovativeness, craftsmanship in experimentation, and perceptiveness and thoroughness in the analysis of experiments. The topographic images which he produced were of the very highest quality and were often exceedingly beautiful.

Lang was born in 1924 at St Annes-on-Sea in Lancashire. He obtained first class honours in a London external BSc in Physics at the University College of the South West (now Exeter University) in 1944, a London external MSc in 1947 and a Cambridge PhD in 1953. He worked in industrial research in England (at Lever Brothers and Unilever Ltd) and in the United States (at the Philips Laboratories, Irvington-on-Hudson, New York).

From 1954 he was Assistant Professor of Physical Metallurgy at Harvard University before moving to a Lectureship in Physics at Bristol University in 1960. Lang spent the remainder of his career in Bristol, gaining promotion to Reader in 1966 and Professor of Physics in 1979. Lang was elected a Fellow of the Royal Society in 1975 and was awarded the society's Hughes Medal in 1997.

Even after retirement in 1987, Lang's dedication to research and scholarship was evidenced by his scientific productivity, his support of younger colleagues and his continual presence in the Physics Department at Bristol. He was a keen amateur geologist and a generous donor to charities.

A.M. Moore and R. Evans



Andrew Richard Lang, physicist: born St Annes-on Sea, Lancashire 9 September 1924; Research Assistant, Cavendish Laboratory, Cambridge University 1947-48; Research Assistant, North American Philips 1952-53; Instructor, Harvard University 1953-54, Assistant Professor of Physical Metallurgy 1954-59; Lecturer in Physics, Bristol University 1960-66, Reader 1966-79, Professor 1979-87 (Emeritus); FRS 1975; died Bristol 30 June 2008.

News
people Emma Watson addresses celebrity nude photo leak
News
Katie Hopkins appearing on 'This Morning' after she purposefully put on 4 stone.
peopleKatie Hopkins breaks down in tears over weight gain challenge
News
Boris Johnson may be manoeuvring to succeed David Cameron
i100
News
peopleHis band Survivor was due to resume touring this month
PROMOTED VIDEO
Have you tried new the Independent Digital Edition apps?
News
ebooksAn unforgettable anthology of contemporary reportage
News
people'It can last and it's terrifying'
News
In this photo illustration a school student eats a hamburger as part of his lunch which was brought from a fast food shop near his school, on October 5, 2005 in London, England. The British government has announced plans to remove junk food from school lunches. From September 2006, food that is high in fat, sugar or salt will be banned from meals and removed from vending machines in schools across England. The move comes in response to a campaign by celebrity TV chef Jamie Oliver to improve school meals.
science
Arts and Entertainment
tv
Life and Style
fashionModel of the moment shoots for first time with catwalk veteran
Life and Style
fashionPart of 'best-selling' Demeter scent range
News
i100
Sport
Tom Cleverley
footballLoan move comes 17 hours after close of transfer window
Sport
Alexis Sanchez, Radamel Falcao, Diego Costa and Mario Balotelli
footballRadamel Falcao and Diego Costa head record £835m influx
Life and Style
fashionAngelina Jolie's wedding dressed revealed
News
i100
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating
and  

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Web Developer/UI Developer (HTML5, CSS3,Jquery) London

£55000 - £65000 per annum: Harrington Starr: A Global Financial Service Organi...

Data Scientist (SQL, PHP, RSPSS, CPLEX, SARS, AI) - London

£60000 - £70000 per annum: Harrington Starr: A prestigious leading professiona...

C# Web Developer (C#, MS Dynamics CRM, SQL, SQl Server) London

£40000 - £50000 per annum: Harrington Starr: A Global Financial Service Organi...

Oracle developer- (Oracle, PL/SQL, UNIX/LINUX) - Trade- London

£50000 - £70000 per annum: Harrington Starr: One of the global leaders in prov...

Day In a Page

'I’ll tell you what I would not serve - lamb and potatoes': US ambassador hits out at stodgy British food served at diplomatic dinners

'I’ll tell you what I would not serve - lamb and potatoes'

US ambassador hits out at stodgy British food
Radio Times female powerlist: A 'revolution' in TV gender roles

A 'revolution' in TV gender roles

Inside the Radio Times female powerlist
Endgame: James Frey's literary treasure hunt

James Frey's literary treasure hunt

Riddling trilogy could net you $3m
Fitbit: Because the tingle feels so good

Fitbit: Because the tingle feels so good

What David Sedaris learnt about the world from his fitness tracker
Saudis risk new Muslim division with proposal to move Mohamed’s tomb

Saudis risk new Muslim division with proposal to move Mohamed’s tomb

Second-holiest site in Islam attracts millions of pilgrims each year
Alexander Fury: The designer names to look for at fashion week this season

The big names to look for this fashion week

This week, designers begin to show their spring 2015 collections in New York
Will Self: 'I like Orwell's writing as much as the next talented mediocrity'

'I like Orwell's writing as much as the next talented mediocrity'

Will Self takes aim at Orwell's rules for writing plain English
Meet Afghanistan's middle-class paint-ballers

Meet Afghanistan's middle-class paint-ballers

Toy guns proving a popular diversion in a country flooded with the real thing
Al Pacino wows Venice

Al Pacino wows Venice

Ham among the brilliance as actor premieres two films at festival
Neil Lawson Baker interview: ‘I’ve gained so much from art. It’s only right to give something back’.

Neil Lawson Baker interview

‘I’ve gained so much from art. It’s only right to give something back’.
The other Mugabe who is lining up for the Zimbabwean presidency

The other Mugabe who is lining up for the Zimbabwean presidency

Wife of President Robert Mugabe appears to have her sights set on succeeding her husband
The model of a gadget launch: Cultivate an atmosphere of mystery and excitement to sell stuff people didn't realise they needed

The model for a gadget launch

Cultivate an atmosphere of mystery and excitement to sell stuff people didn't realise they needed
Alice Roberts: She's done pretty well, for a boffin without a beard

She's done pretty well, for a boffin without a beard

Alice Roberts talks about her new book on evolution - and why her early TV work drew flak from (mostly male) colleagues
Get well soon, Joan Rivers - an inspiration, whether she likes it or not

Get well soon, Joan Rivers

She is awful. But she's also wonderful, not in spite of but because of the fact she's forever saying appalling things, argues Ellen E Jones
Doctor Who Into the Dalek review: A classic sci-fi adventure with all the spectacle of a blockbuster

A fresh take on an old foe

Doctor Who Into the Dalek more than compensated for last week's nonsensical offering