ESS Docs Document 193-v1

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Estimation of Residual Dose Rates and Beam Loss Limits in the ESS Linac

Document #:
ESS-doc-193-v1
Document type:
Tech Note
Submitted by:
Jim Stovall
Updated by:
Jim Stovall
Document Created:
07 May 2012, 09:38
Contents Revised:
07 May 2012, 09:38
Metadata Revised:
07 May 2012, 09:38
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Abstract:
The" ESS" linac" will" accelerate" protons" from" rest" to" 2.5" GeV" through" a" variety" of" accelerating"structures.""One"of"the"advantages"of"modern"linear"accelerators"compared"with" their" circular" cousins" is" that" they" can" typically" provide" very" strong" confinement" for" very" high" beam" currents." While" in" the" linac," the" protons" will" be" bunched" and" focused" by" electromagnetic" fields" to" prevent" them" from" striking" the" walls" of" the" accelerator" and" being" lost.""Any"protons"that"escape"these"confining"fields"cannot"be"recaptured"and"will"eventually" interact"with"the"parent"materials"from"which"the"linac"is"constructed"via"various"processes." The" nuclear" reactions" between" the" errant" protons" and" the" atoms" of" the" parent" materials" of" the"accelerator"will"result"in:""
•"inLsitu"production"of"ionizing"radiation"fields"(prompt"radiation)"and"
•"the"production"of"radioactive"nuclei"inside"the"parent"material"(induced"activity).""
In"this"report"we"address"only"the"induced"radioactivity"in"which"radioactive"isotopes" are" produced" within" the" accelerator" structures." These" isotopes" decay" by" emitting" neutrons," alphas,"betas"and"gammas"until"they"reach"the"“valley"of"stability.”"Since"the"halfLlives"of"the" radioactive" isotopes" can" range" from" fractions" of" seconds" to" years" and" beyond," the" radiation" fields" will" always" be" present" in" the" machine" once" it" becomes" operational" and" will" become" the"source"of"residual"dose"rates"to"which"ESS"workers"may"be"exposed."
The"purpose"of"this"report"is"to"evaluate"the"residual"dose"rates"resulting"from"proton" beam" losses" in" the" RFQ" (radiofrequency" quadrupole)" and" DTL" (drift" tube" linac)" sections" of" the" ESS" accelerator." Based" on" these" results" we" propose" beam" loss" criteria" that" can" be" used" by" accelerator" designers" that" will" ensure" residual" activation" levels" in" the" early" part" of" the" accelerator," which" will" be" consistent" with" safe" handsLon" maintenance" as" defined" by" statutory" regulations," ESS" administrative" requirements" and" best" practice" in" the" accelerator" community."
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