Walton 13

17 19

Seamus Fitzgerald Lismore Community School Waterford, Ireland

Wetenschappelijke experimenten tijdens de Wereldoorlog II

The Life and Work of Ernest Walton

Ní raibh an coincheap do dhaoine ag cur smacht The concept of humans controlling the building blocks of nature, being able to take some of its ar na blocanna tógadh don nádúr, a bheith ábalta awesome power and transforming it to something roinnt cumas uamhnach a thógáil agus é a we can command was no more than a theoretical claochlaigh do rud faoi smacht ach coincheap concept at the dawning of the last century. Due to teoiriciúil ag an tús don aois seo chaite. De dheasca the inspirational efforts of some pioneering na h’iarrachtaí ionspioráideach tá roinnt eolaí scientists however, these theories began to be ceannródaíochta áfach, thosaigh na teoiricaí seo ag tharlú, agus mar seo realised, opening the d’oscail na geataí-tuile mar floodgates for a new era of ré nua don fionnachtain. discovery. One such Bhí Ernest Walton ar an scientist was Ernest T. S. liosta den eolaíoht seo, Walton, who is seen by agus dar le lear mór many as one of sciences daoine, is fíor-laoch don true heroes. eolaíocht é. It all began in Thosaigh gach rud I Dungarvan, a town on the Dún Garbháin, baile ag south east coast of Ireland, an cósta deisceart-oirthear when, on the 6th of na h’Éirinn, nuair a rugadh October 1903, Ernest Thomas Sinton Walton Ernest Thomas Sinton Walton ag an séú lá de was born. His mothers name was Anne E. Sinton mhí Deireadh Fomhair, and his father, John 1903. Anne E Sinton is ainm dá mháthair agus Walton, was a Methodist ministir Modhach ba ea a minister. h’athair, John Walton. De They had to move bharr an Ministreacht, every few years however due to the ministry. As a d’fhiach said a aistriú gach ERNEST T. S. WALTON result, young Ernest found cúpla bhliain. De bharr himself at the other end of Ireland for his school seo, bhí Ernest ag an ceann eile d’Éireann da days, attending day schools in Cambridge (Co. laethannta scoile, ag freastal ar scoile laethannta i Cambridge (co. Dún) agus Cookstown (co. Tír Down) and Cookstown (Co. Tyrone). His mathematical and scientific brilliance really Eoghain). Thosaigh a niamh eolaíoch ag loinnú sna began to shine through while he was a boarder at the h’ábhair Matamaitic agus eolaíoch nuair a bhí sé ag Methodist College in Belfast. freastail ar Coláiste Modhach i mBéal Feirste. His college years took off, when in 1922 he went Thosaigh a bhlianta coláiste nuair a d’fhreastal sé ar

epm

38

epm

17 19

EPM

History of Science and Technology

to Trinity College, Dublin on a scholarship, and Choláiste Trinity i mBaile Átha Cliath le after four years he graduated with first class honours scoláireacht agus cailíonn sé bhaint amach le chéim onórach sna Matamaitic agus Fisic Teoiricúil. An in maths and experimental physics. The following year, as Ernest Walton was bhliain dar gcionn, nuair a bhí Ernest Walton ag receiving a M.Sc, degree, saw the continuation of fágáil a chéim M.Sc., leanann ré an- corraithe agus one of the most exciting and significant eras in the tábhachtach I stair na fisic. Rinne Rutherford fhionnachtain history of dochloite don physics. mion-núicléas There was sa bhliain Rutherford’s 1910, agus tar compelling éis sin, discovery of d’fhoilsigh the miniscule Niels Bohr atomic nucleus conas a fhitis in 1910, an lucht followed by d i ú l t a c h Niels Bohr’s timpeall an revelation of núicléas, how electrons chomh mhaith orbit the leis an cur síos nucleus in ar na hadaimh 1913, as well agus cáithnín a s fo-adamh Heisenberg’s, déanta ag Dirac’s, and Heisenberg, Schrödinger’s Dirac agus f u r t h e r Schrödinger, description of 1934 CYCLOTRON sa bhliain 1925 atoms and subagus 1926, a t o m i c chun trácht a dhéanamh air. particles in 1925 and 1926, to name but a few. Leanann an By 1927, the momentum continued to build, as much of the research seemed to converge on the moiminteam de bhliain 1927, agus is cosúil gur díriú formhór den taighde ag an núicléas a bhriseadh atomic nucleus. What scientists all over the world were racing to le spléacadh isteach, agus an bhealach is fearr chun do, was to disassemble the nucleus to peer inside, é a dhéanamh ná é a ionsú le cáithníní bídeach ag the best way to do this being to strike it with a fast bogadh co tapaidh, cosúil le piléar ag briseadh vása moving tiny particle, almost like a bullet shattering a i smidiríní. vase. Walton ar Cambridge Ag an bhliain sin, d’fhág Ernest Walton chun Walton at Cambridge That very year, Ernest Walton set sail for freastal ar h’ollscoil Cambridge, cáilúil le n’eólaí,

epm

39

epm

17 19

EPM

History of Science and Technology

Cambridge University, famous for its scientists, boasting such names as Sir Isaac Newton, Charles Darwin, and more recently, Stephen Hawking. Walton soon found himself working under the previously mentioned and ever eminent Lord Rutherford. There, Walton’s first job was to build an apparatus designed to accelerate electrons (negatively charged particles) to very high speeds. Even though Ernest poured his flowing ingenuity into the project, and there was some success, the electrons did not quite reach the speeds desired. Then in 1929, he began the development of a new apparatus to accelerate positively charged particles to high speeds. For this he was joined by Sir J.D. Cockcroft, another superb scientist with a boundless scientific capacity.

ag maíomh as n’ainmnigh mar Sir Isaac Newton, Charles Darwin, agus ar na mallaimh, Stephen Hawking. Bhí Walton ag obair faoi an fear céimúil, Lord Rutherford, luaithe roimhe seo. Ba é an chéad tasc a fuair sé, ná gléas a tógadh chun cáithníní le lucht diúltach a géaraigh an luas. Cé go raibh sé ag obair go dian sa tionscadal, agus bhí roinnt conách, níor shroich na lucht diúltach chomh luath go leor. Ansin, i 1929, thosaigh sé an forbairt don gléas nua chun lucht deimhneach a géaraigh an luas faoi lánluas. Do tasc seo, sé páirtí nua, Sir John Cockcroft, eolaíeile le intinn hiontach freisin.

An tUasal J.D. Cockcroft Nóta gearr anois faoi Cockcroft; Rugadh sé i 1897, go teaglach traidisiúnta de déanaigh cadás, sa Todmorden I Sasana. D’fhreastail sé ag Chéad Cogadh ann Domhain tar éis le staidir déanta sa mata, agus Sir J.D Cockcroft The following is a d’fhill sé níos déanaí very brief note about chun an innealtoireacht Cockcroft; Sir John leictreas a staidir. Ach I Douglas Cockcroft was greann tamaillín bhí sé th born on May the 27 féin ag obair sa 1897, to a family of Cambridge faoi Lord traditionally cotton Rutherford freisin, go manufacturers at hádhúil. Má bhfuil spéis Todmorden, England. agat, tar éis a hobair le He served in World Walton, rinne sé taighde War 1 after studying ar an radar, agus chaith SCANNED AT THE AMERICAN INSTITUTE OF PHYSICS mathematics, and sé treimhse ag obair I g afterwards returned to Ceanada agus sna Stáit study electrical engineering. Aontaithe ar feadh tamaill. Bhí sé pósta le cúigear It was not long before he too fortuitously found pháiste. himself at Cambridge, also working under Lord Sé an faighteoir Rutherford in the Cavendish Laboratory. inmholta de a lán duaiseanna agus onóir a rí nuair a You may be interested to know that following bhí sé níos sine. Ach ar ais arís go 1932, faighimid

epm

40

epm

17 19

EPM

History of Science and Technology

his work with Walton, he worked on radar research, and he also worked in Canada and the U.S. for a time. He was married and had five children. He was the deserving recipient of many awards and honours in his later life. Reversing back to 1932, we find ourselves in a year where the seeds of years of hard work and meticulous experimentation finally flourished to fruition. That year saw James Chadwick’s discovery of the neutron, Carl Anderson’s discovery of the positron, Fermi’s announcement of his theory of radioactive Beta decay, and of course, Ernest Walton’s and J.D. Cockcroft’s splitting of the atom. How Physics Was Changed Forever Their proton accelerator was carefully built in a neglected room in the Cavendish Laboratory. Once again, Walton’s innate resourcefulness was fully utilised as the pioneering pair of scientists relied partially on old car batteries and bits of petrol pumps! Even with these meagre resources, they somehow managed to build an apparatus capable of developing an accelerating voltage of up to 700,000 volts, used to accelerate protons to colossal velocities. Finally, despite their challenges, on April 14th 1932, Walton and Cockroft succeeded. They did it. As their proton accelerator bombarded a Lithium target, releasing Alpha particles and energy, they became the first people in history to bring about the transmutation of the nucleus of an atom using artificially accelerated particles. For the first time ever, man had the ability to change the universes fundamental building block, the atom. Surely this was a peerless feat at the time. •In the apparatus, protons released from a Hydrogen discharge tube were shot into the accelerating tube. •These protons were accelerated by the very high voltage, down through a vacuum.

epm

sa bhliain nuair a bhláth go hiontach sa síol den obair crua agus turgnaimh cúramach. Sa bhliain sin, d’fhionn James Chadwick an neutron, d’fhionn carl Anderson an positron, d’fhógair Fermi a theoiric den lobh Beta radaighiomhach, agus at ndóigh, scoilt Ernest Walton agus J.D. Cockcroft an adamh. Conas a Athraigh an Fisic Go Deo

WORKING ON HIS PARTICLE ACCELERATOR

Thóg said an luasaire proton go cúramach sa seomra faillithe sa saotharlann Cavendish. Arís eile, d’úsáid Walton a hachmhainnaí nádúrtha mar bhraith na dhá eolaí ceannródaíoch leathain at sean cadhnraí carr agus píosaí den caidéalaí peitril! Cé nach raibh ach achmhainnaí gortach acu, ar dhóigh éigin thógadh said gléas bheith inniúil 700,000 voltaí a dhéanamh den voltas luathaigh, bheith cleachta le protons a luathaigh de luas ollmhór. Faoi dheireadh, d’ainneoin na ndeacaractaí uile acu, d’éirigh Walton agus Chadwick sa 14ú lá de mhí

41

epm

17 19

EPM

History of Science and Technology

•They hit a Lithium target, which was angled at 45˚ to the incoming proton beam. The products of the reaction moved out at an angle of 90˚ to the beam, where they struck Zinc sulphide screens which gave off microscopic flashes of light (scintillations). When they experimentally showed that it was Alpha particles (two protons and two neutrons) released, the reactions equation was; Lithium (three protons and four neutrons) + Hydrogen (one proton) → Helium (two protons and two neutrons) + Helium (two protons and two neutrons) + Energy Walton was the first to observe this reaction, using a microscope. When their results were published later that month, its importance was embraced by the world with the respect it deserved. Their work was very important for various reasons. It was one of the most significant developments in the foundation of the branch of physics involving controlled accelerated particles. Subsequent developments encompass many of the original Walton-Cockcroft principals. It was the first experimental verification of the equation E = mc², developed by Einstein which shows the relationship mass has with energy. In this experiment, the sum of the masses of the Alpha particles was less than the total mass of the Lithium and protons used. This means that mass was converted into energy. •The Walton-Cockcroft accelerator provided many times more high velocity protons than the Alpha particles used by Rutherford to achieve nuclear transmutation from the available radioactive material from naturally occurring sources. This experiment also verified the new wave mechanics predictions and validated Gamov’s calculations. Walton the Laureate

epm

Aibreáin, 1932. Rinne siad é. Nuair a bhuail a luasaire proton sprioc Lithium, agus cáithníní Alpha a scaoileadh, d’éirigh siad na chéad daoine riamh a hathraigh an núicléas adamhach le húsáid cáithníní Alpha a scaoileadh, d’éirigh siad na chéad daoine riamh a hathraigh an núicléas adamhach le húsáid cáirhnaí luathaigh saorga. Den chéad úair riamh, bhí ábalta ar an cine na bunúsach píosaí den cruinne a hathraigh, an adamh.go deimhin, bhí an éacht seo gan cothrom ag an am. •Sa ghléas seo, scaoile protons as feadán folmhaigh hidrigin agus d’urchaidh siad isteach sa feadán luathaigh. •Luathaigh na protons seo den voltas luathach aird, síos thrí folús. Bhuail siad sprioc Lithium, ar fiar de 45˚ leis an ga proton ag teacht. Bhogadh na toraí den imoibriú amach ar fiar de 90˚ leis an ga, agus bhuail siad scáileán Sinc sulphide ag scaoilte splanc micreascópadd solas (scintillations). Nuair a mhustaigh siad le trialach go raibh siad cáithnínaí Alpha (dhá protons agus dhá neutrons) scoilte, bhí an cothromóid mar an imoibriú; Lithium (trí protons agus ceithre neutrons) + Hidrigin (proton amháin) → Helium (dhá protons agus dhá neutrons) + Fuinneamh Bhí Walton an chéad fhear an imoibriú seo a coimhéad, micreascóip a úsáideann. Nuair a d’fhoilsigh na toraí níos déanaí sa mhí, shnaidhm an domhan a tábhactas ina chéile leis an meas a thuilleadh é. Bhí a hobair an-tábhachtach mar réasúnta éagsúla; Bhí an forbairt seo an-tábhachtach mar an bunn den craobh fisic a bheith gafa i cáithníni luathaigh. Tá a lán gnéithe den prionsabalaí Walton-Cockcroft le feicáil sna forbairthe iartheachtach. Bhí sé an chéad uair a fíoraigh an cothromóid E = mc², forbairthe don Einstein, a thaispéain an baint ag toirt le fuinneamh. Sa triail seo, bhí an iomlán toirt den cáithníní Alpha níos lú ná an iomlán toirt den Lithium a úsáid. Mar seo, d’athraigh toirt go fuinneamh. •Chuir an luasaire Walton-Cockcroft ar fail protons níos tapaidh ná na cáithníní Alpha a úsáid

42

epm

17 19

EPM

History of Science and Technology

For his far reaching contribution to the world of science, Ernest Walton was the worthy recipient of the 1951 Nobel Prize for physics, jointly with John Cockcroft. Later on, Walton was to lecture from 1934 right up until his retirement in 1974. In 1934, Professor Walton married Freda Wilson. Their four children, following in Ernest’s footsteps, all have science related jobs. During World War two, Walton was privately asked by James Chadwick (the discoverer of the neutron) to go to the United States and join a gathering of workers for ‘war work’, which turned out to be no less than the Manhattan project! For his own various reasons, however, he decided not to leave Ireland. Professor Walton passed away on June 25th 1995, but he is still vividly remembered. He was noted, not only for his experimental genius, but also as an engaging and excellent lecturer who had the ability to captivate his listeners through his presentation of often complex topics in an understandable form. As well as being a shy and modest man, he is said to have had a resilience and unrelenting motivation to abide by his deeply rooted principals. One of the true heroes of science. Bibliography http://nobelprize.org/nobel_prizes/physics/ laureates/1951/walton-bio.html w w w . i r i s h s c i e nt i s t . i e / 2 0 0 2 / c o n t e n t s . a s p ? contentxml=02p14.xml&contentxsl=is02 pages.xsl http://janus.lib.cam.ac.uk/db/node.xsp? id=EAD%2FGBR%2F0014%2FWLTN http://groups.iop.org/HP/Archive/No17p18.htm http://understandingscience.ucc.ie/pages/ sci_ernestwalton.htm www.ulsterhistory.co.uk/walton.htm

den Rutherford, chun athraigh núicléach a bhain amach den ábhar radaighníomhach ó foinsigh nádúrtha. D’fhíoraigh an triail seo na thuairaigh nua meicnic agus réitigh sé n’áireaimh Gamov. Walton an Laureate Dé bharr a shíntiús tábhachtach don domhain an eolaíocht, fuair Ernest Walton an duais Nobel sa Fisic sa bhliain 1951, le chéile le John Cockcroft. Níos déanaí, léacht Walton ó 1934 go dtí a scor i 1974. sa bhliain 1934, phós Professor Walton le Freda Wilson. Ag leanann sa coiscéim a athair, tá postanna eolaíocht ag a ceathrar pháiste. I rith dara cogadh an Domhain, d’iarraigh James Chadwick (an fionnan don neutron) a Ernest Walton faoi rún, dul go dtí na Sáit Aontaithe chun claráigh le gasra oibrí mar ‘obair cogadh’, agus d’fhoilsigh sé níos déanaí, go raibh an obair sin an scéim Manhattan! Mar cúis éagsúla, áfach, shocraigh sé nach Éirinn a fágaidh. Fuair Professor Walton báis sa cúig lá is fiche de mhí meitheamh sa bhliain 1995, ach tá a cuimneadh beo fós. Bhí aird air, ní amháin mar a bua trialach, ach mar léachtóir mealltach agus ar dóigh le ábaltacht aige chun a héisteoirí a tharraing thrí a bronnadh den ábhair casta i cruth le tuiscint chomh mhaith le sin, fear achmhainneach le spreagadh gan stad chun seas lena deargphrionabalaí. Fíor-laoch don éolaíocht. Clár leabhar http://nobelprize.org/nobel_prizes/physics/ laureates/1951/walton-bio.html w w w . i r i s h s c i e nt i s t . i e / 2 0 0 2 / c on t e nt s . a s p ? contentxml=02p14.xml&contentxsl=is02 pages.xsl http://janus.lib.cam.ac.uk/db/node.xsp? id=EAD%2FGBR%2F0014%2FWLTN http://groups.iop.org/HP/Archive/No17p18.htm http://understandingscience.ucc.ie/pages/ sci_ernestwalton.htm www.ulsterhistory.co.uk/walton.htm

Acknowledgements My sincerest gratitude firstly to my physics

epm

43

Buíochas le

epm