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    SLAC KLYSTRON LECTURES

    Lecture 2

    January 21, 2004

    Kinematic Theory of Velocity Modulation

    George Caryotakis

    Stanford Linear Accelerator Center

    [email protected]

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    K!"MATC T#"$%& $' V"L$CT& M$()LAT$!

    In this sectin an! in the ne"t, #e $resent the thery %ehin! the $rinci$a& 'r(u&ae use! in the

    !esi)n ' a($&i'ier *&ystrns+ The intent is t $ri!e the stu!ent r en)ineer #ith the assu($tins use! in their

    !eriatins s that he r she can use the( crrect&y+ These assu($tins resu&t in the a$$r"i(atins necessaryt !erie ana&ytica& e"$ressins 'r the )ain an! %an!#i!th ' *&ystrns at &# r' si)na& &ee&s -s(a&&.si)na&/+

    The athca! c!e, #hich is !iscusse! in a &ater &ecture, cntains such 'r(u&ae+ The thery %e&# is inc&u!e!

     %ecause it is inc($&ete&y cere! in te"t%*s, an! %ecause there is #i!es$rea! cn'usin n h# t $r$er&y

    treat cu$&in) ce''icients an! %ea( &a!in) in c($&e" caities+ This is a $r%&e(, $articu&ar&y at (i&&i(eter

    #ae 're3uencies, #here e"ten!e! interactin caities are &i*e&y t %e use!+

    Other c!es, such as AJ.!is* an! AIC, si(u&ate *&ystrn $er'r(ance usin) 'irst $rinci$&es

    -e&ectrn !yna(ics an! a"#e&&5s e3uatins/+ These c!es are a$$r"i(ate n&y t the e"tent that they areeither ne.!i(ensina& -r t# !i(ensina&/, r e($&y t carse a )ri!, r cntain ther a$$r"i(atins+

    Later &ectures !escri%e these c!es, as #e&& as t# #r*in) *&ystrn e"a($&es, in ne case c($arin) actua&

     $er'r(ance t resu&ts 'r( three !i''erent c!es+ This is essentia& in'r(atin, since *&ystrn !esi)n in the

    21st century is %ein) carrie! ut a&(st entire&y n c($uters -i+e+ #ith &itt&e, r n c&!.testin) r %ea(

    testin)/+

    The *ine(atic -n s$ace char)e/ ana&ysis %e&# '&&#s seera& authrs #h $u%&ishe! %*s n

    *&ystrns shrt&y a'ter 662+ The e&city (!u&atin -r %unchin)/ 2.caity thery that '&&#s i((e!iate&y

    is the n&y &ar)e si)na& ana&ytica& treat(ent ' *&ystrns in this cha$ter+ It &ea!s t the 7esse& 'unctince''icients ' the current har(nics an! a ca&cu&atin ' t#. caity a($&i'ier e''iciency+ The su%se3uent

    !eriatin ' the cu$&in) ce''icient an! the state(ent ' the %ea(.&a!in) 'r(u&ae are %ase! n s(a&& si)na&

    a$$r"i(atins, #hich are a&i! 'r a&& %ut the 'ina& caities ' a (u&ticaity *&ystrn+ Neither treat(ent ta*es

    s$ace char)e int accunt+ This is !ne in the thir! &ecture ' the series+

    A&& ca&cu&atins in this an! the ne"t &ecture are nn.re&atiistic+ The 'r(u&ae use! in si(u&atins in

    &ater &ectures are hi)h&i)hte! in ye&&#+

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    Cnsi!er a *&ystrn cnsistin) ' t# caities, a

    %uncher an! a catcher, %th )ri!!e!+ -8i)+1/+ Let a

     %ea( ' e&ectrns, #hich has %een acce&erate! %y a

     $tentia& 9 t a e&city  u, traerse the 'irst $air '

    )ri!s, #here it is acte! u$n %y an r' &ta)e 91sinωt,

    re!uce! %y a cu$&in) ce''icient + The &atter(!i'ies the &ta)e acrss the )ri!s t $r!uce the

    e''ectie &ta)e (!u&atin) the e&ectrn %ea(+

    E"$ressins 'r the cu$&in) ce''icient -aays &ess

    than 1/ #i&& %e !erie! &ater+

    2

    0 0

    1

    2mu eV  =

      #here the e&ectrn char)e e !es nt carry its #n ne)atie si)n+ The e&ectrn ener)y is (!i'ie! %y the r'

    'ie&! at the )a$ an! the '&&#in) re&atinshi$ can %e #ritten 'r the e"it e&city u:

    2 2

    0 1

    1 1sin

    2 2mu mu eMV t  ω − =

    -1/

    -2/

    'r( -1/ an! -2/, it '&&#s,

    10

    0

    1 sin MV 

    u u t V 

    ω = + -;/

    Fig. 1

    The e&ectrns in the %ea( enter the )ri!!e! )a$ #ith ener)y,

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    I' #e assu(e that 91/

    10

    0

    1 sin2

    t  MV 

    u uV 

      ω    ÷  

    ≅ +

    -

    ?/

    @ is the %unchin) $ara(eter, an! θ0=ω&=u0+O%ius&y, #hen @ 1, ωt2 is (u&tia&ue! an! there ise&ectrn erta*in)

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    1 2o t  I dt I dt =  6e hae, !i''erentiatin) ->/

    2

    11 1 cs

    dt 

     X t dt  ω = −

     8r( -B/ an! -/, can n# #rite

    2 1=- = /t o I I dt dt =

      An!, re$&acin) !t2=!t

    1 %y its a&ue in E3+ -D/

    -B/

    -C/

    -D/

    1-1 cs /

    ot 

     I  I 

     X t ω =

    −-10/

    The 3uantity ' char)e &eain) the %uncher in the ti(e intera& t 1  t t 1 +dt 1  is  I odt 1, #here  I o  is the

     %ea( C current enterin) the %uncher+ This char)e, a'ter !ri'tin), enters the catcher in the intera& t 2 t

    t 2+dt 2+ I' It -tta& current, !c an! r'/ is the current trans$rte! %y the %ea( t the entrance t the catcher,

    then thru)h cnseratin ' char)e,

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    8r @ F 1, the current at the catcher %ec(es in'inite, since %y ins$ectin ' 8i)+ 2, the 'inite char)e

    trans$rte! 'r( the %uncher at t1 F 0 arries at the catcher in a Ger ti(e intera& -!t 2=!t1 F 0 at t1 F 0/

    T ca&cu&ate It, ne (ust then su( the a%s&ute a&ues ' a&& current cntri%utins t I

    t  'r( ti(e

    se)(ents t11

    , t12

    , etc, at the %uncher as '&&#s,

    0

    11 12

    1 1++++

    1 cs 1 cst  I I 

     X t X t ω ω 

    = + +

    − − -11/

    Fig 3(5)

    The current #ae'r(s at the %uncher are sh#n in 8i)+ ; %e&#

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     N#, since I t  is c&ear&y a $eri!ic 'unctin ' Ht, it can %e e"$an!e! in a 8urier series, as '&&#s,

    2 0 2 01

    I cs - / sin - /Jt o n n

     I I a n t b n t ω θ ω θ  ∞

    = + − + −∑the ce''icients are )ien %y,0

    0

    2 0 21= cs - / - /n t a I n t d t  

    θ π 

    θ π 

    π ω θ ω  

    +

    = −∫ an!

    0

    0

    2 0 21= sin - / - /n t b I n t d t  

    θ π 

    θ π 

    π ω θ ω  

    +

    = −∫ 

    -12/

    -1;/

    -14/

    Usin) an! -B/ a%e, #e can n# #rite

    01 1 1cs - sin / - /n

     I a n t X t d t  

    π 

    π 

    ω ω ω π  −= −∫ 

    an!

    01 1 1

    sin - sin / - /n

     I b n t X t d t  

    π 

    π 

    ω ω ω π  −

    = −∫ 

    -1?/

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    There're, the catcher r' current I t  can %e #ritten as the '&&#in) series

    0 0 1 0

    1

    2 - /cs - /t n I I I J nX n t ω θ ∞= + −∑

    The n F 1 har(nic -the 'un!a(enta&/ is si($&y,

    0

    1 0 1 0

    - /

    0 1

    2 - / cs- /

    Re 2 - /  j t 

     I I J X t 

     I J X e  ω θ 

    ω θ 

    = −

    =

    Fig 4(5)

    -1B/

    -1/

      %n is i!entica&&y e3ua& t Ger, since the inte)ran! a%e is an !! 'unctin ' t 

    1.

    It turns ut that the e"$ressin -1?/ 'r the an ce''icients is a&s a re$resentatin ' the 7esse&

    'unctins ' the 'irst *in! an! nth r!er -8i)+ 4/+

    -1>/

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    6hen @

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    is $r%a%&y the (st i($rtant $ara(eter use! in the !esi)n ' a *&ystrn %ecause the *&ystrn

    )ain is a 'unctin ' 2n -#here n is the nu(%er ' caities/, an! %ecause it is ery sensitie t the %ea(

    !ia(eter, #hich is neer *n#n $recise&y+ ence !iscre$ancies in the ca&cu&ate! r si(u&ate! )ain ' a

    *&ystrn can %e usua&&y trace! t inaccuracies in +

    6e %e)in #ith the e3uatin ' (tin ' the e&ectrn in a )ri!!e! )a$ 'ie&! EG-G,t/, !e'ine! as

    #here E( is the (a"i(u( a&ue ' the e&ectric 'ie&! in a caity interactin )a$ that e"ten!s 'r( G

    F 0 t G F !+ The 'unctin '-G/ is a sha$e 'actr+ The (a"i(u( r' &ta)e acrss the )a$ is

     A $ara(eter -'r s(a&&.si)na& a

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    I' the 'ie&! in the )a$ #ere Ger, an! the e&ectrn e&city u0, the e&ectrn $sitin a'ter ti(e t #u&! %e

    G F u0t+ Since the r' (!u&atin is s(a&&, #e can #rite, a$$r"i(ate&y

    0   - /u t z h z  α = +

    6e n# intr!uce βe F H =u0 , the %ea( $r$a)atin 'actr+ The 'unctin h-G/ is in!eter(inate 'rur $ur$ses an! !es nt enter in the ca&cu&atins that '&&#+ Then -24/ %ec(es,

    u&ti$&y n# %th si!es ' -2;/ %y 2!G an! %tain the !eriatie ' the s3uare ' the e&city, as '&&#s

    22

    1

    22 2 - /   j t 

    V dz d z d dz edt dt f z e dz  

    dt dt dt dt d m

    ω   = = ÷  

    Inte)ratin) 'r( G F 0 t a !istance G #ithin the )a$

    2

    210

    0

    2 - /

     z 

     j t V dz eu f z e dz  dt d m

    ω 

      − = ÷     ∫ Su%stitutin) -2?/ int -2B/, inte)ratin) t the en! ' the )a$ -G F !/ an! !entin) the e"it e&city %y u,

    #e hae

    2 2   10

    0

    1- / - /

    2

    e

     j z V m u u e f z e dz  

    β − = ∫ 

    et z ω β ≅

    -24/

    -2?/

    -2>/

    -2B/

    -2/

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     N# reca&& E3+ -2/, re$r!uce! %e&#,

    2 2

    0 1

    1 1

    2 2  eff  mu mu eMV eV  − = =

    #hich e"$resse! the chan)e in *inetic ener)y ' an e&ectrn a'ter )in) thru)h a narr# )a$,

    #ith a &ta)e 91  acrss it -ti(e !e$en!ence (itte!/+ 9

    1, #hen (!i'ie! %y the cu$&in)

    ce''icient , yie&!s the e''ectie &ta)e actin) n the e&ectrns+ 6e n# hae an accurate

    e"$ressin 'r + In a ne.!i(ensina& syste( it is, %y -21/, -2/ an! -2D/, The e''ectie

    &ta)e is then,

    0- /   e

     j z 

    eff z  V E z e dz  β 

    = ∫ an!,

    1   0

    1- / - /   e

     j z 

    e z  M E z e dz V 

    β β    = ∫ 

    0

    0

    - /

    - /

    - /

    e

     j z 

     z 

    e   d 

     z 

     E z e dz 

     M 

     E z dz 

    β 

    β    =∫ 

    ∫ 

    -2D/

    -;0/

    -;1/

    -;2/

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    -;;)

    -;4/

    E3+ -;2/ can %e )enera&iGe! %y e"ten!in) the inte)ratin er the entire G.a"is+ It can then %e

    a$$&ie! t 2.!i(ensina& -)ri!&ess )a$, as in 8i)+ ? %e&#/

    The cu$&in) ce''icient can then %e #ritten,

    1

    - /

    e j z 

     z 

    eff 

    e

     z 

     E e z V 

     M V 

     E dz 

    β 

    β 

    −∞∞

    −∞

    = =∫ 

    ∫ In #r!s, is e3ua& t the cn&utin ' the a"ia& e&ectric 'ie&! E-G/ #ith the e"$nentia& e MβeG 

    -the e''ectie &ta)e/, !ii!e! %y the &ta)e -inte)ra& ' the 'ie&!/ acrss the )a$+

     Nte a&s, that i' the 'ie&! EG-G/ is a $iece#ise cntinuus 'unctin ' G, it can %e #ritten in

    ter(s ' the inerse 8urier inte)ra&,

    1- / - /

    2e j z 

    e z  g E z e dz β β 

    π 

    −∞

    = ∫ 

    #hich (eans that can %e a&s #ritten in ter(s ' the 8urier trans'r( ' the e&ectric 'ie&!

    1

    2- / - /e e M g 

    π β β = -;?/

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    -;>/

    -;B/

     8r (st cases, #here the 'ie&! can %e c($ute! e"act&y #ith c!es such as SUER8IS r A8IA

    -see Cha$ter 10/, an! #here the 'ie&! is an een 'unctin ' G, a ery si($&e e"$ressin resu&ts+

    cs

    - /

     z e

    e

     z 

     E z 

     M  E dz 

    β 

    β 

    −∞ ∞

    −∞

    =

    ∫ 

    ∫ 

    A$$&yin) it t the case ' a )ri!!e! )a$ #ith a cnstant 'ie&! ' (a)nitu!e EG F9

    1=! %et#een !=2

    an! !=2 -an! shi'tin) the ri)ina& ri)in/, #e %tain the #e&&.*n#n e"$ressin

    1

    2

    1

    2

    - / sin1 2- / cs

    2

    e j z    d  e z 

    e eed 

    V  d  E z e dz d 

     M zdz d V d 

    β  β 

    β β β 

    −∞

    = = =∫ 

    ∫ 

    This ca&cu&atin !e(nstrates the use ' a si($&i'ie! 'r( 'r the cu$&in) ce''icient #hen the

    'ie&! ' interactin is an ana&ytic 'unctin ' G+ In c($uter si(u&atins, the 'ie&! ' an e"ten!e!

    interactin caity can %e !eter(ine! %y si(u&atin, &iste! in E"ce& -'r e"a($&e/ #ith cs-% eG/ an!c($ute! usin) E3+-;4/ 'r sy((etrica& 'ie&!s, an! -;1/ 'r ar%itrary 'ie&! !istri%utins+ This is a (uch

     %etter (eth! 'r ca&cu&atin) , i' the caity interactin 'ie&! is *n#n in !etai&+

    K&ystrn en)ineers )enera&&y ! nt re&y n -;B/ t !esi)n their tu%es, %ut rather e($&y (re

    accurate, t#.!i(ensina& (!e&s+ T !erie a 2.!i(ensina& e"$ressin 'r the cu$&in) ce''icient

    in un)ri!!e! cy&in!rica& !ri't tu%es, ne (ust: a/ assu(e a certain e&ectric 'ie&! at the e!)e ' the )a$ at

    r F a, c($ute! 'r( the !etai&e! nature ' the !ri't tu%e ti$s, r !eter(ine! %y si(u&atin, an!

    ca&cu&ate at r F a, %/ 'r( that %un!ary cn!itin, c($ute as a 'unctin ' r thru)hut theinteractin re)in, an! c/ aera)e the cu$&in) ce''icient er the %ea(+

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    The )a$ 'ie&! is !e'ine! as %e're, this ti(e #ith an r.

    !e$en!ence:

    - , , / - , /   j t  z m E r z t E f r z e  ω =

    an! at r F a,

    - , , / - , /   j t  z m E a z t E f a z e  ω =

     9arius authrs hae a(use! the(se&es er the years c($utin) cu$&in) ce''icients 'r run!

    ti$s, *ni'e.e!)e ti$s, s3uare ti$s, etc+ 6arnec*e P uenar!4 assu(e !ri't tu%es en!in) in *ni'e.e!)es t %tain the e"$ressin %e&# 'r the 'ie&! at the )a$, at the !ri't tu%e ra!ius a+

    1

    2

    1- , /

    1

     z 

    V  E a z 

    d   z 

    π =

     − ÷

     

    8i) ?

    -;/

    -;D/

    -40/

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    Usin) the ear&ier 'r(u&a in E3+ -;1/

    1

    21 10 0

    1 1 1- , / - , /

    1

    e e

    d d 

     j z j z 

    e z 

    V  M a E a z e dz e dz 

    V V d   z 

    β β β π 

    = =  − ÷  

    ∫ ∫ 

    6ith a )! ta%&e ' inte)ra&s, #e %tain the (st c((n&y use! cu$&in) ce''icient at r F a,

    0- , /2

    ee

    d  M a J 

      β β 

       =   ÷  

    In the a%sence ' s$ace char)e an! 'r 'ie&! aryin) sinusi!a&&y #ith ti(e in a acuu(,

    a"#e&&5s e3uatins re!uce t the #ae e3uatin,

    22

    ,   2 2

    1 z r z z 

     z 

     E  E  c E 

    ∂∇ = ∂

    #here c is the e&city ' &i)ht+ Su%stitutin) 'r( -4?/,

    22

    2

     z  z 

     z 

     E  E 

     E ω 

    ∂= −

    ∂#e hae,

    2 2

     z z  E k E ∇ = −#here * F #=c+ I' the ariatin #ith G is as eMβG, then,

    2 2 2- /r z z 

     E k E β ∇ = −

    -41/

    -42/

    -4;/

    -44/

    -4?/

    -4>/

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    Since, un&i*e in a c&se! #ae)ui!e, the a"ia& e&ectric 'ie&! cannt %e Ger n a"is at the center ' the )a$,

    the s&utin t -?0/ cannt %e a J0, %ut an I

    0 7esse& 'unctin, #hich is nt Ger at r F 0 as J

    0 is+ This (eans that

    β* -r that #ae the $hase e&city u is &#er than c an! the a$$r$riate 'unctin is Ι0(γ r )e MβG, #ith,

    2 2 2k γ β = −

    Since the a"ia& 'ie&! is c($&ete&y s$eci'ie! at the sur'ace r F a, it can %e !escri%e! as a

    8urier inte)ra& er %, 'r any a&ue ' r insi!e that sur'ace

    ( )

    ( )0

    0

    - , , / - / j t j z  z  I r 

     E r z t e g e d  I a

    ω β γ  

    β β γ  

    ∞−

    −∞

    = ∫ #here, as %e're, %ut n# as a 'unctin ' r as #e&&,

    1- , / - , /

    2

     j z 

     z  g r E r z e dz β β 

    π 

    −∞

    = ∫ 

    ( )

    ( )0   - /

    0

    - , / - , /   e j z  z  I r 

     E r z g r e d  I a

    β β γ   β β γ  

    ∞−

    −∞

    = ∫ 

    -4B/

    -4/

    -4D/

    -?0/

    Let us n# 'in! the e''ectie $tentia& -inte)ra& ' the 'ie&! e"$erience! %y an e&ectrn

    trae&in) #ith the %ea( e&city u0at a ra!ius r a&n) a &ine $ara&&e& t the a"is+ Let the e&ectrn

    enter the )a$ at t F 0+ Since ω t β e z the e&ectric 'ie&! at r, G is

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    Let us n# inte)rate er G , at an ar%itrary ra!ius r t %tain the e''ectie $tentia& 9e'' 

    , as in E3+

    -;;/+ 

    ( )

    ( )

    0   - /

    0

    - , /   e j z 

    eff  

     I r V dz g r e d  

     I a

    β β γ   β β 

    γ  

    ∞ ∞−

    −∞ −∞

    =

    ∫ ∫ 6e #i&& n# use the '&&#in) i!entity:

    - /2 - /e

     j z 

    ee dz β β  πδ β β  

    ∞−

    −∞

    ≡ −∫ The !e&ta 'unctin δ-β

    e.β/ has the $r$erty that, #hen (u&ti$&ie! %y anther 'unctin ' β, an!

    inte)rate! er β 'r( (inus t $&us in'inity, it returns that 'unctin ea&uate! at βe+ Cnse3uent&y,

    ( )

    ( )

    ( )

    ( )0 0- /

    0 0

    - , / 2 - , / - /e j z 

    eff e

     I r I r V dz g r e d g r d  

     I a I a

    β β γ γ  β β π β δ β β β  γ γ  

    ∞ ∞ ∞−

    −∞ −∞ −∞

    = = −∫ ∫ ∫ 

    an!,

    ( )

    ( )

    ( )

    ( )0 0

    0 0

    2 - , / - / 2 - , /e

    e e

    e

     I r I r  g r d g r 

     I a I a

    γ γ  π β δ β β β π β  

    γ γ  

    −∞

    − =∫ 

    -?1/

    -?2/

    -?;/

    -?4/

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    19

    #here, )e2 F β

    e2  * 2+ Then,

    ( )

    ( )0

    0

    - , / 2 - , /  e

    eff e e

    e

     I r V r g r  

     I a

    γ  β π β 

    γ  =

    an!

    ( )

    ( )0

    1 1 0

    - , /   1- , / 2 - , /

    eff e   e

    e e

    e

    V r    I r  M r g r 

    V V I a

    β    γ  β π β 

    γ  = =

    #h

    ere,   2 2 2

    e e   k γ β = −6e #i&& n# !r$ the e su%scri$t 'r ) 'r( this $int n, #ith the un!erstan!in) that ) #i&& aays %e

    re$resente! %y E3+ ?B an! #i&& aays %e rea&, #here *&ystrns -r T6Ts/ are cncerne!+ On the ther

    han!, it is cnentina& in (st te"t%*s t *ee$ the su%scri$t e in βe F H=u

    0+  N#, ea&uatin) 9

    e''at r

    F a, an! c($arin) #ith -;?/ an! -42/

    ( )( )

    0

    0

    0

    - , / - /2

    ee

     I r d  M r J  I a

    γ  β β γ  

    =

    #hich is the )enera& e"$ressin 'r the cu$&in) ce''icient at ra!ius r insi!e a )ri!&ess cy&in!rica& )a$ '

    ra!ius a an! #i!th !+

    -??/

    -?>/

    -?B/

    -?)

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    20

     Nte that the tta& cu$&in) ce''icient is the $r!uct ' the cu$&in) ce''icient a at r F a,

    an! aer 

     #hich re$resents an aera)in) ' the cu$&in) ce''icient er the %ea( crss.sectin+

    I', instea! ' %tainin) -42/ 'r( an ana&ytic e"$ressin ' the a"ia& e&ectric 'ie&! at r F a, #e

    %taine! that 'ie&! %y si(u&atin an! use! -;;/ t ca&cu&ate a cu$&in) ce''icient at r F a, #e#u&! (u&ti$&y the resu&t #ith a ca&cu&ate!

    aer + re )enera&&y, then

    2 2

    0 1

    00

    - / - /- = 2/

    - /a a!er e

     I b I b M M M J d 

     I a

    γ γ  β 

    γ  

    −= =

    S(e ty$ica& nu(%ers 'r the $ara(eters use! in ea&uatin) : I' %e! F1, )a F 1 an! %=a F 0+>, #e

    %tain a F 0+B>?,

    aer  F 0+>D an! F 0+?;+

    -?D/

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    21

    2

    0   4

    b e

    e

     M ""

    β β 

    ∂= −∂

    E3uatin ->0/ is 3uite )enera& an! a$$&ies t a&& )a$ sha$es, as #e&& as t the e"ten!e! r

    sheet %ea( caities that #i&& %e !iscusse! &ater+ Its (eanin) is that the rati ' the %ea( &a!in)

    cn!uctance  %  an! the %ea( cn!uctance

    0  F -I

    0=9

    0/ is entire&y !eter(ine! %y the cu$&in)

    ce''icient an! its ariatin #ith the C %ea( &ta)e+ In the ne"t &ecture, #e #i&& see that the

    (a)nitu!e ' the cu$&in) ce''icient in e"ten!e! caities is $ti(iGe! %y synchrniGin) the

     $hase e&city ' the e"ten!e! caity t the %ea( e&city, an! that the sta%i&ity ' these caities

    !e$en!s n a $sitie  %=

    0

    Usin)  ->0/ #ith an! a &itt&e !i''erentia& ca&cu&us, #i&& eri'y the %ea( &a!in) 'r(u&a 'r

     $&ane )ri!!e! )a$s,

    0

    sin = 2 sin = 21 cs = 22 = 2 = 2

    b e ee

    e e

    " d d  d " d d 

    β β  β β β 

      = −  

    2 2

    0 1

    0

    - / - /

    - /a

     I b I a M M 

     I a

    γ γ  

    γ  

    −=

    ->1/

    ->0/

    ->2/

    T cnc&u!e this &ecture, #e nee! t $ri!e a 'r(u&a 'r the %ea( &a!in) cn!uctance  %+

    Reca&& that in E3+ -2?/ a%e, ter(s in #ere nt inc&u!e! in the !eriatin ' + It turns ut that

    ca&cu&atin 'r %ea( &a!in) re3uires these t %e ta*en int accunt, an! the !eriatin ' an

    e"$ressin 'r  %  %ec(es ery cu(%ers(e+ 6e #i&& state the resu&t %e&# an! e"$&ain it

    3uantitatie&y+

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    22

      I' the e"$ressin -?/ 'r #ere (ani$u&ate! as in E3+ ->1/ t %tain  %=  'r thecy&in!rica& nn.)ri!!e! )e(etry, an! the resu&t #ere then aera)e! er the %ea(, a ery

    c($&icate! e"$ressin 'r %ea( &a!in) #u&! resu&t+ Such a 'r(u&a #u&! a&s %e rather

    &i(ite! in its a$$&icatin, since the resu&t #u&! nt %e a$$&ica%&e t e"ten!e! )a$s+ A %etter

     $rce!ure #i&& %e !escri%e! in Lecture 4+

      A *&ystrn caity e3uia&ent circuit, inc&u!in) the %ea( &a!in) cn!uctance -an!

    susce$tance/ is sh#n in 8i)+ > %e&#+ A a&ue 'r 7 %  is $ri!e! in the 6arnec*e %*+ The

    !etunin) e''ect is s(a&& an! ca$acitie+

    Fig 6

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    23

    [1] Feenberg, E., “Notes on Velocity Modulation,” Sperry Gyroscope Lab. Report 5521-1043,

    Sperry Gyroscope o., !nc., Garden ity, N", Sept #$, 1%&$.

    [#] Fre'lin, (. )., *. +. Gent, . -. . -etrie, -. (. +allis, and S. G. /o'lin, “-rinciples o0Velocity Modulation,” IEEE Journal   %, -art !!! *, 1%&2, -g. 34$5%14.

    [] 6ranc7, G. M. (r., “Electron 6ea' oupling in !nteraction Gaps o0 ylindrical Sy''etry,”

    IRE Trans. on Elec. De ., May, 1%21, -g 1%5#82.

    [&] +arnec9e, ., and -. Guenard, Les Tubes Electron!"ues a #o$$an%e par &o%ulat!on %e

    '!tesse( -aris: Gaut7ier Villars, 1%$%.

    [$] Ge;arto;s9i, (. +., and +atson ). *.,)r!nc!ples o* Electron Tubes( . Van Nostrando'pany, !nc. 1%2$.


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