High Brightness Electron Beam Diagnostics and their ... - CASA
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High Brightness Electron Beam Diagnostics and their ... - CASA

High Brightness Electron Beam Diagnostics and their ... - CASA High Brightness Electron Beam Diagnostics and their ... - CASA

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etatronexcitationaspicturedingure3.5.Anexampleofmeasurementforthesixcorrector eachotherisapproximately60degsothatonecanaccuratelyprobethewholeperiodofthe 0F00H 0F00V 300 0F08H 0F04V 0F04H 0F08V Figure3.5:Betatronphaseadvancebetweeneachcorrectorusedtoperturbtheorbitalongthe latticeinthehorizontal(leftplot)andvertical(rightplot)plane(100meterscorrespondsap- 200 proximatelytotheendofthebacklegbeamline). 100 theoneeectivelyproducedaccordingtothedierenceorbitanalysisisapproximately10%.After aforementionedispresentedingure3.6.Itisexperimentalresponsewiththelatticeandsimulated 0 0 20 40 60 80 100 0 20 40 60 80 100 inclusionofthisdiscrepancyinthemodel,thenewlycomputedpattern(seegure3.7)areingood fortheverticalplane).Inthepresentcase,itwasfound5thatoneofthequadrupoleswasnot varyinthemodeldierentmagneticelementsandtrytominimizea2-typequantitiesdenedas: producingthemagneticgradientthatitwassetto;thediscrepancybetweenthesetgradientand response.Althoughthetwopatternsgenerallymatchquitewellonecanseeinthecaseofcorrector 2F04Hthattherearelargediscrepancies.Atechniqueusedtondoutthediscrepanciesisto 2x=PNi=1(xmeasured i xsimu i)2forthehorizontalplane(thesamekindofquantityisdened Distance from Cryomodule Exit (m) beusedtodescribeaccuratelythelattice. 3.3.4ResultsonDispersionMeasurement Aswehavealreadymentioned,thedispersionmeasurementtheoreticallyreducestothemeasure- agreementwiththemeasurementindicatingthemodel(secondorderbasedtransfermatrix)can mentoftheorbittransversedisplacementforagivenenergychange.Theeasywayofvaryingthe energyintheacceleratoristochangetheacceleratinggradientortheinjectionphaseofonecavity. Unfortunately,therearetransverseeldsintheCEBAFcavitythatcansignicantlydeectthe 5D.R.Douglasrstnotedthisfact Betatron Phase Advance (Deg)

∆ x (mm), Corrector 0F00H ∆ x (mm), Corrector 0F04H x 10−3 5 0 −5 0 x 10−3 5 20 40 60 80 100 ∆ y (mm), Corrector 0F00V x 10−3 5 0 −5 0 x 10−3 5 20 40 60 80 100 0 0 −5 −5 0 20 40 60 80 100 0 20 40 60 80 100 x 10−3 x 10−3 5 5 problemfortheoperatingenergiesoftheIRFEL:simulationsindicatestheinduceddeectiondueto gradientchangeissignicantandcanbeoftheorderoffewtensofmrad.Wehaveexperimentally Figure3.6:Comparisonbetweenthemeasuredandsimulatedlatticeresponseforthesixcorrectors veriedsuchresultinourpreliminarymeasurementofdispersionintheback-legtransferlineby usedduringthedierenceorbitmeasurement(100meterscorrespondsapproximatelytotheendof thebacklegbeamline). beam6.BecausethisRF-induceddeectionisinverselyproportionaltothebeamenergyitcanbea 0 0 andcompareitwiththecasewhereweoperatethecavityattheirnominalgradientanduseda −5 −5 0 20 40 60 80 100 0 20 40 60 80 100 (whichisinfacttheR12-inducedpattern)isreproduced.Thisresultconrmsoursuspicionthat varyingthecavitygradient.Wepresentingure3.8thebeampositionosetalongthebeamline correctoratthelinacexittosimulatepotentialRF-inducedsteering:thesametypeofpattern Distance (meters) Distance (meters) approximately500100mforamagneticeldvariationof1%insuringthespuriousdispersion therecirculationarc.Wenotethatthemaximumtraversedisplacementofthebeamcentroidis islowerthan5cminabsolutevalue.Thisisanimportantresultforemittancemeasurementaswe shallseeinChapter4. dispersionmeasurementsperformedusingRF-gradientvariationisnotvalid.Nextwepresent,in gure3.9,ameasurementofdispersionobtainedbyvaryingthemagneticeldinallthedipolesof 6AdetailedstudyofthiseectispresentedinChapter6 ∆ x (mm), Corrector 0F08H ∆ y (mm), Corrector 0F04V ∆ y (mm), Corrector 0F08V

etatronexcitationaspicturedingure3.5.Anexampleofmeasurementforthesixcorrector eachotherisapproximately60degsothatonecanaccuratelyprobethewholeperiodofthe<br />

0F00H<br />

0F00V<br />

300 0F08H<br />

0F04V<br />

0F04H<br />

0F08V<br />

Figure3.5:Betatronphaseadvancebetweeneachcorrectorusedtoperturbtheorbitalongthe latticeinthehorizontal(leftplot)<strong>and</strong>vertical(rightplot)plane(100meterscorrespondsap-<br />

200<br />

proximatelytotheendofthebacklegbeamline).<br />

100<br />

theoneeectivelyproducedaccordingtothedierenceorbitanalysisisapproximately10%.After aforementionedispresentedingure3.6.Itisexperimentalresponsewiththelattice<strong>and</strong>simulated<br />

0<br />

0 20 40 60 80 100 0 20 40 60 80 100<br />

inclusionofthisdiscrepancyinthemodel,thenewlycomputedpattern(seegure3.7)areingood fortheverticalplane).Inthepresentcase,itwasfound5thatoneofthequadrupoleswasnot varyinthemodeldierentmagneticelements<strong>and</strong>trytominimizea2-typequantitiesdenedas: producingthemagneticgradientthatitwassetto;thediscrepancybetweenthesetgradient<strong>and</strong> response.Althoughthetwopatternsgenerallymatchquitewellonecanseeinthecaseofcorrector 2F04Hthattherearelargediscrepancies.Atechniqueusedtondoutthediscrepanciesisto 2x=PNi=1(xmeasured i xsimu i)2forthehorizontalplane(thesamekindofquantityisdened<br />

Distance from Cryomodule Exit (m)<br />

beusedtodescribeaccuratelythelattice. 3.3.4ResultsonDispersionMeasurement Aswehavealreadymentioned,thedispersionmeasurementtheoreticallyreducestothemeasure- agreementwiththemeasurementindicatingthemodel(secondorderbasedtransfermatrix)can<br />

mentoftheorbittransversedisplacementforagivenenergychange.Theeasywayofvaryingthe energyintheacceleratoristochangetheacceleratinggradientortheinjectionphaseofonecavity. Unfortunately,therearetransverseeldsintheCEBAFcavitythatcansignicantlydeectthe 5D.R.Douglasrstnotedthisfact<br />

Betatron Phase Advance (Deg)

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