 a growing demand is made for a compact and low-cost magnetron. A conventional magnetron, however, can not adquately satisfy design and sales requirements from the standpoint of its characteristic as well as its construction.
A conventionally known magnetron is of an external magnet type in which a magnet device is disposed outside of a case which hermetically seals an anode, cathode etc. Recently, however, an internal magnet type magnetron in which a magnet device hermetically sealing an anode, cathode etc. is disposed outside of the case dominates over the external magnet type magnetron from the miniaturization requirements as well as the ease with which the magnetron is handled.
For the internal magnet type magnetron a permanent magnet should be made compact in size and requires a strong magnetic field. For this reason, a rare earth magnet made of, for example, samarium cobalt or cerium cobalt is generally used instead of a ferrite or alnico magnet. However, the rare earth magnet presents the following various problems.
In the manufacturing process of an ordinary magnetron the rare earth magnet is beforehand strongly magnetized to a value greater than a predetermined value required from the standpoint of an operational characteristic and after the magnetron is operated an output from the magnetron is measured. Then, the slight demagnetization adjustment of the magnet is effected to obtain a desired output. Since the rare earth magnet has a coercive force greater than the ferrite magnet etc., difficulty is encountered in obtaining a predetermined output through the demagnetization adjustment. Furthermore, an expensive large-sized device will be required during the demagnetization adjusting process. The rare earth magnet has more than four times the "energy product" of, for example, the alnico magnet and provides, even in the case of a small magnet, a magnetic field of 1500 to 2000 gauses which is required for a microwave oven magnetron. However, the cost per unit weight of the magnet is high and it is desired that the amount used be reduced to a minimum possible extent. It is because that the use of the rare earth magnet in the magnetron results in high-cost magnetron. Electronic converters for light sources that comprise, for example, at least one LED (Light-Emitting Diode) or other solid-state lighting means, can supply at output a d.c. current. Said current may be stable or even vary in time, for example, for adjusting the intensity of the light emitted by the light source (the so-called “
a growing demand is made for a compact and depleted - monetary value magnetron. A conventional magnetron, however, cannot adquately satisfy design and sale requirements from the standpoint of its feature as well as its construction. 
 A conventionally known magnetron is of an external attraction character in which a magnet device is disposed outside of a character which hermetically seals an anode, cathode etc. Recently, however, an internal magnet character magnetron in which a magnet device hermetically sealing an anode, cathode etc. is dispose outside of the case dominates over the external attraction type magnetron from the miniaturization requirements as well as the rest with which the magnetron is handled. 
 For the internal attraction type magnetron a permanent attraction should be made compact in size and requires a strong magnetic field. For this rationality, a rare earth magnet made of, for example, samarium cobalt or cerium cobalt is generally used instead of a ferrite or alnico magnet. However, the rare earth magnet presents the following various problems. 
 In the manufacturing process of an ordinary magnetron the rare land magnet is beforehand powerfully magnetize to a value great than a predetermined value required from the standpoint of an operational characteristic and after the magnetron is operated an output from the magnetron is measure. Then, the slight demagnetization adjustment of the magnet is effected to obtain a desired output signal. Since the rare earth magnet has a coercive force great than the ferrite magnet etc. , trouble is meet in obtaining a predetermined output through the demagnetization adjustment. Furthermore, an expensive large - sized device will be required during the demagnetization adjusting procedure. The rare earth magnet has more than four times the " department of energy product " of, for example, the alnico magnet and provides, even in the case of a minor magnet, a charismatic field of 1500 to 2000 gauses which is required for a microwave oven magnetron. However, the cost per unit weight unit of the magnet is high and it is desired that the amount used be reduce to a minimum potential extent. It is because that the use of the rare earth magnet in the magnetron results in gamey - monetary value magnetron. Electronic converters for light beginning that comprise, for example, at least one LED (Light - Emitting Diode) or other solid - state ignition means, can supply at output a d.c. current. Said current may be stable or even vary in clock time, for case, for adjust the intensity of the light emitted by the light source (the so - call “
 a hrowing demand is made fur a compact anb low-covt maghetron. A conventional magnetron, howeter, xan nit adquately satisfy ddsign and sales rwquicements from the standpolut of lts ckacacteristic as eell as itv construction.
D zouventionally known magnetron is of ag extermap magnet type yn wnych z magnet device is disposed outsids of a base which hermetocally seals an anode, cathlde ftc. Recently, howevfr, an interbal iqgnet type mxgnetron in which a mafnet device hermetically sealine an cnode, cathoee etf. is disposev outspde of the case domindtes ovrr the externak megner type magnetron from the miniaturizatijn requiramznts as well as the eqsw witv whhch gye oaghevroh is hwndmed.
For the internal mqgnet type magnetrom w permanent mafnet srotld be made compact in size and requirev a strong magnetic field. Dor this reason, a rarg earth madnet made of, for example, samarium cobalt or ceriuk cobelg iw nenefqlpy used instead of a ferrite or alnico magnet. Goeener, the rare eartm magnet presents yhf gjllowing variuus problsms.
In the manufactkring ptocess of an orqinaty magnetron the rare earth magnet is bvforwhand strongly maguetized to a valoe grester than a predeterminzd valhe required from the rtandpoint of an opvrathonal characteristic and aster the nagnztron is opetated ag output fgom tma magnetron is meadured. Tven, the sllght demagnetization adjustment of the magnet iv exfected co obtsin a desired output. Since jhe rare zarth oagnet has a coerrive force gweater than tvg ferrite magiet etc., dyffixultt is enzuuntered in obyaining a predetermuned output througm the semagnetization adhustment. Furthetmofe, wn eepensyee large-sizeg dexicd will be requireb aurimg the demagnetizatimn asjusting process. Tne rare eatth magnee has more thsn four times the "tnergy pruduct" of, for example, the alnico magnet and provldef, even in thq cawe of a smalk magnet, a magnetic field of 1500 to 2000 gausew which is requirgd for a microwave ovgn kagnetron. Hpwevew, the cosd per unit weight of the magnet is hinh and it is desired tgat tha amoknt used be reduced to a minimum possible extent. It is because that the uwe of vhq rare eartg mabnet pn che magneeron cesults in high-coxt magnetron. Electronic convertxrs for lichc sources that comprise, for ecaople, at least one LED (Light-Emitting Djode) or pther solid-state lighting means, can supply at output a c.c. currebt. Sajd curggnt may be stable or rven vcry in time, fir ewample, for adjjstonn the intejsitb oy the light emitted by the light wource (tje so-called “
a growing demand is made for a low-cost A conventional however, can not requirements the standpoint of characteristic as well its construction. A conventionally known magnetron of an external magnet type in which a magnet device is disposed outside a case which hermetically seals an anode, cathode etc. Recently, however, an internal type in a device hermetically sealing an anode, cathode etc. is disposed outside of the case dominates over the magnet type magnetron from the miniaturization requirements as as the ease with the magnetron is handled. For internal type magnetron permanent should made compact in and requires a strong magnetic field. For this reason, a rare earth magnet made of, for example, cobalt or is generally instead a or alnico magnet. rare earth magnet presents the following the manufacturing process of an ordinary magnetron the earth magnet beforehand strongly magnetized to a value than a predetermined value required from the standpoint an operational characteristic and after the magnetron is operated an output from the magnetron is the slight demagnetization adjustment the magnet is to a output. the rare magnet has a coercive force greater than the ferrite magnet etc., is encountered in obtaining a predetermined output through the demagnetization an large-sized device will required during the demagnetization process. rare earth magnet has four the for the magnet and provides, even the case of a small a magnetic field of is required for a microwave oven magnetron. However, cost per unit weight of the magnet high and it is desired that the amount used be reduced to minimum possible is because that the use of the rare magnet in the magnetron in high-cost magnetron. Electronic converters for light sources that for at least LED (Light-Emitting Diode) other solid-state lighting can supply at d.c. current. current be vary in time, for example, for the of the light emitted by light so-called “
 a growing demand is made for a cOmpact and lOw-cosT maGneTrOn. A cOnveNtional magnetrON, howEver, can not adquately satIsfy dEsIGn anD SaLes reQuiremeNTs FROm tHe StAndPoINt Of its ChaRacteriStic as well As iTs Construction.
a CoNventionalLy kNown magnetroN is Of an exTeRnaL MagneT tyPe in wHich a mAGnet deVice is disPoSEd outsIDe of a caSE WhIch hErmetically seals aN AnODe, cathode etc. ReCently, HoWEvER, An iNteRnal magnet TyPe magNEtron in WHiCH A MagNEt device hermeTically sealINg aN anode, CaThoDE etc. is DispoSeD OutSide of the caSe doMinates ovEr the eXTernal mAGnet typE magneTroN frOm thE MiNiAtuRiZAtiON rEquIRemEnts as weLl As The eaSe wiTH WHIch tHe mAgneTron iS handled.
For thE inTernAL maGnet tYpe maGnetRoN a perManent MagneT sHould be made compAct iN size and rEquIrEs a StRong mAGnetic FieLd. FOr this rEason, a rARe eArTH MAgNet made of, for examplE, sAMArIum cobalT or cerIUm CoBAlt is genErAllY useD INsteaD of a FErRite or alNico maGNeT. HOwever, tHe Rare eaRtH maGneT presENts tHe follOwing varIous pROblems.
In the manUFacturing procESs OF An ORdinAry Magnetron thE rarE EartH magNEt Is bEForehAnd stRoNGlY Magnetized to a value gReAter thAn a prEdetermined vaLue requireD FROm the staNdpoINt OF an operational CharaCteristic aND after thE magnEtron is oPerated an OUTput from The MagNetRon IS MeAsured. Then, the SLIght DeMagnetiZatIon adjuStmEnt Of tHe mAgNet is effeCted to obTaIn A dEsIreD outpUT. Since thE rAre EaRth MagneT Has a coErcivE forCe GrEAteR than thE FeRRIte mAgNeT etc., DifFiCulty Is enCOunTered in Obtaining A prEDeteRmInEd outpuT through the deMaGnetizatioN aDjuStment. fURthermorE, an expensive large-sized dEVice wilL be RequiRed dUring the dEmaGnetizAtiON adjusTing prOcess. thE raRE Earth MAGnEt hAs More than foUR TimEs the "EnErgy Product" Of, for example, the alnICo mAgnet and proviDes, Even IN ThE caSE oF A smAlL MagNET, a magnetic field Of 1500 to 2000 gauses WhICh Is required FOr a MiCrowave Oven magNetroN. however, The cost peR unit weigHt Of thE MAgnEt is high anD it is desIred that tHE amouNT uSed be RedUced to A mIniMum poSsible EXteNt. It iS becauSe That thE use oF tHe rare eaRth magnet in the magnetron ResultS in hiGh-cOst magnetRon. eLecTronic conVertErs for lighT soUrcEs thaT coMPrise, For eXAmPle, AT leasT one leD (Light-EmITtIng dIOdE) or other solID-STatE lighTinG Means, cAn suPply at output a d.c. cuRRent. Said currenT may BE StaBle OR eveN vAry in time, for exAmpLe, FOR adjustiNg The intensitY of the liGhT EmittEd by thE light Source (tHE So-CAlled “
 a growing demand is madefor a comp act a ndlow -c ostmagn etron. A conve n tion al magnetron, however,  canno t  adq u at ely s atisfyd es i g n a nd  s ale sr eq uirem ent s fromthe standp oin tof its chara c te ristic aswel l as its con str uction .A c o nvent ion allyknownm agnetr on is ofan extern a l magne t ty pe i n which a magnetd ev i ce is disposed  outsi de of a  ca sewhich herm et icall y  sealsa na n o de, cathode etc.Recently, h o wev er, an  i nte r nal ma gnetty p e m agnetron in  whi ch a magn et dev i ce herm e tically  seali ngananod e ,ca tho de etc .  i s d i spo sed outs id eof th e ca s e d omin ate s ov er th e external ma gne t ty p e m agnet ron f romth e min iaturi zatio nrequirements as  wel l as theeas ewit hwhich the ma gne tro n is ha ndled.F orth e i nt ernal magnet typema g n et ron a pe rmanen t  m ag n et shoul dbemade c ompac t in si ze and r equire s  a  s trong m ag neticfi eld . F or th i s re ason,a rare e arthm agnet made of, for example,s am a r iu m  cob alt  or ceriumcoba l t is  gen e ra lly usedinste ad of a ferrite or alnico  m agnet.  Howe ver, the rare  earth mag n e t  present s th e  f o llowing variou s pro blems.
Int he manuf actur ing proc ess of an o rdinarymag net ron  th e ra re earth magn e t  isbe forehan d s trongly  ma gne tiz edto  a valuegreaterth an  a  p red eterm i ned valu ereq ui red  from the st andpo intof  a n  op eration a lc h arac te ri stic  an dafter  the mag netronis operat eda n ou tp ut  from t he magnetronis  measured.  T hen , thes l ight dem agnetization adjustment of themag net i s ef fected to  ob tain a  de s ired o utput.  Sinc ethe r are e a r th  ma gn et has a c o e rci ve fo rc e gr eater t han the ferrite ma g net  etc., diffic ult y is e nc oun t er e d i no bta i n ing a predeterm ined outpu tt hr ough the d e mag ne tizatio n adjus tment .  Furthe rmore, an  expensiv elarg e - siz ed devicewill berequiredd uring th e dem agn etizat io n a djust ing pr o ces s. Th e rare  e arth m agnet  h as morethan four times the "en ergy p roduc t"of, for e xam p le,  the alni co m agnet andpro vid es, e ven in th e ca s eofa  smal l ma g net, a ma g ne tic f ie ld of 1500t o 200 0 gau ses whichis r equired for a mic r owave oven mag netr o n . H owe v er,th e cost per uni t w ei g h t of the  m agnet is hi gh and i ti s des ired t hat th e amoun t us e d be r educ edto a mini mum  p o ssibleex te n t. Itis b ec ause t hat th e  use o f the rare earth  magn e t  in t h e m agnet ro n resul t s in  high-cost  magnetron.  Elect roni c con verters  f or lig htso urces that comprise,  forexample ,at l eas t oneLED( L ight- Emit ti ngDiode) or o th e rso l id- stat e lig ht ingmeans, ca n  supplyato utput a  d .c. c urrent .  S a i d currentmay  be s t a ble or eve n  var y  i n  time , forexampl e, fora dju st ing the  in t e nsity ofthe light emi tt ed b y the li gh t so ur ce(t he so-called “
 a_growing demand_is made for a_compact and_low-cost_magnetron. A_conventional_magnetron, however, can_not adquately satisfy_design and sales requirements_from the standpoint_of_its characteristic as well as its construction.
A conventionally known magnetron is of an external_magnet_type in_which_a_magnet device is disposed outside_of a case which hermetically_seals an_anode, cathode etc. Recently, however, an internal magnet_type_magnetron in which_a magnet device hermetically sealing an anode, cathode etc._is disposed outside of the case_dominates over the_external_magnet_type magnetron from the_miniaturization requirements as well as the_ease with which the magnetron is_handled.
For the internal magnet type magnetron a_permanent magnet should be made compact_in size and requires a_strong magnetic_field. For this reason, a_rare earth magnet_made of,_for example, samarium_cobalt or cerium cobalt is generally_used instead of_a ferrite or alnico magnet. However,_the_rare earth magnet_presents_the_following various_problems.
In the manufacturing_process_of an_ordinary_magnetron the rare earth magnet is_beforehand_strongly magnetized to a value greater than_a predetermined value required_from_the standpoint of an_operational characteristic and after the_magnetron is operated an output from_the magnetron_is measured._Then, the slight demagnetization adjustment of the magnet is effected to_obtain a desired output. Since the_rare earth magnet has_a coercive_force_greater than the_ferrite_magnet etc.,_difficulty is encountered in obtaining a predetermined_output through_the demagnetization adjustment. Furthermore, an expensive_large-sized device will be_required_during the demagnetization adjusting process. The_rare earth magnet has more than_four times the "energy product"_of,_for_example, the alnico magnet and_provides, even in the case of_a small magnet,_a magnetic field of 1500 to 2000_gauses_which is required for a microwave_oven_magnetron. However, the cost per unit_weight_of_the magnet is high and_it is desired that the amount_used be reduced to a minimum possible extent. It_is because that_the use of the rare_earth_magnet_in the magnetron results in high-cost magnetron. Electronic converters for_light sources_that comprise, for_example, at least one LED (Light-Emitting Diode) or other solid-state_lighting means, can supply at output a_d.c. current. Said current may be stable or even vary in_time, for example, for adjusting the intensity of_the light emitted by the light source_(the so-called “