RE: STAR HFT beam pipe From: Howard Wieman <HHWieman@lbl.gov> To: Wolfram Fischer <Wolfram.Fischer@bnl.gov> Date: Sep 7 2005 - 9:00am Wolfram,And what is the risk? Will the beam pipe be destroyed?Howard-----Original Message-----From: Wolfram Fischer [mailto:Wolfram.Fischer@bnl.gov] Sent: Tuesday, September 06, 2005 5:38 PMTo: HHWieman@lbl.govSubject: Re: STAR HFT beam pipeHoward,I should have pointed this out more explicitly. If oneoperates at the minimum aperture requirement, one is thelimiting aperture.For radii between 15 and 20mm, the risk estimate is abit more involved. In this range IP6 is not in the shadowof IP4, but could be in the shadow of the injection andabort kicker (this depends on the orbit details in allthese areas).WolframHoward Wieman wrote:> Wolfram,> > > > Thanks for the note.> > > > In your previous check we were not the limiting aperture. Is this > change the result of including the vertical orbit offset?> > > > Howard> > > > -----Original Message-----> *From:* Wolfram Fischer [mailto:Wolfram.Fischer@bnl.gov]> *Sent:* Tuesday, September 06, 2005 4:51 PM> *To:* HHWieman@lbl.gov> *Cc:* roser@bnl.gov; hseuh; Ptitsyn, Vadim; Trbojevic, Dejan; Bai, Mei> *Subject:* Re: STAR HFT beam pipe> > > > Howard,> > the animation drawing is quite nice. Here I summarize what we have > discussed last> Thursday (with slight modifications) regarding a possible small beam > pipe at the STAR IP:> > (1) Physical aperture> We require a 5mm vertical orbit offset and at least 7 transverse rms > beam sizes as> physical aperture. This gives an aperture of 16mm (at injection with Au > beam of> 15mm.mrad emittance, the most limiting scenario).> > Thus a beam pipe radius of 15mm over a length of about 0.5m appears just > possible.> However, this beam pipe *_will become the limiting physical aperture > vertically_*.> And losses that we now typically encounter at the injection or abort > kicker, or in IR4> where a beam pipe with 19mm vertical aperture is installed, may end up > at IP6.> These losses typically happen during the injection setup, or transition > crossing. You must> be able to withstand this. Note that our loss monitors near the > injection and abort kickers> are desensitized during injection and transition crossing, something > STAR may wish to> avoid in the future. (Currently the STAR loss monitor input into the > beam permit system> is masked out according to Mei.)> > To ensure that IP6 it is not the limiting physical aperture, the radius > needs to be increased to> 20mm (given the same amount of orbit errors in all the limiting > locations). It would> then be in the shadow of the IR4 element near the IP with 19mm vertical > aperture.> > (2) Vacuum requirements> We would like to have a NEG coated beam pipe that can be activated (i.e. > it needs> to be bakable to 250C). The allowable dynamic pressure must be specified > by the> experiments (based on allowable beam-gas background considerations). The > vacuum> design must be approved by Dick Hseuh.> > (3) Impedance> To avoid any impedance problems transitions should be smooth.> This is the case in the attached electronic drawing.> > Let me know if I can help you any further,> > Wolfram> > > > Howard Wieman wrote:> > Hi Wolfram,> > > > Here is the model of the beam pipe: > http://www-rnc.lbl.gov/~wieman/TopBeamPipe4.exe > <http://www-rnc.lbl.gov/~wieman/TopBeamPipe4.exe>> > > > You can down load this and run it in windows. There is a measure tool > to get dimensions. As you will see the lengths are a little different > than what I communicated to you from memory. The diameter of the bigger > diameter pipe is 57 mm, smaller than I told you.> > > > Thanks,> > Howard> > > > > -- > > Wolfram Fischer> > Brookhaven National Laboratory> > Bldg. 911B, Upton, NY 11973, USA> > Tel. +1-631-344-5452> -- Wolfram FischerBrookhaven National LaboratoryBldg. 911B, Upton, NY 11973, USATel. +1-631-344-5452
From: Howard Wieman <HHWieman@lbl.gov> To: Wolfram Fischer <Wolfram.Fischer@bnl.gov> Date: Sep 7 2005 - 9:00am
Wolfram,And what is the risk? Will the beam pipe be destroyed?Howard-----Original Message-----From: Wolfram Fischer [mailto:Wolfram.Fischer@bnl.gov] Sent: Tuesday, September 06, 2005 5:38 PMTo: HHWieman@lbl.govSubject: Re: STAR HFT beam pipeHoward,I should have pointed this out more explicitly. If oneoperates at the minimum aperture requirement, one is thelimiting aperture.For radii between 15 and 20mm, the risk estimate is abit more involved. In this range IP6 is not in the shadowof IP4, but could be in the shadow of the injection andabort kicker (this depends on the orbit details in allthese areas).WolframHoward Wieman wrote:> Wolfram,> > > > Thanks for the note.> > > > In your previous check we were not the limiting aperture. Is this > change the result of including the vertical orbit offset?> > > > Howard> > > > -----Original Message-----> *From:* Wolfram Fischer [mailto:Wolfram.Fischer@bnl.gov]> *Sent:* Tuesday, September 06, 2005 4:51 PM> *To:* HHWieman@lbl.gov> *Cc:* roser@bnl.gov; hseuh; Ptitsyn, Vadim; Trbojevic, Dejan; Bai, Mei> *Subject:* Re: STAR HFT beam pipe> > > > Howard,> > the animation drawing is quite nice. Here I summarize what we have > discussed last> Thursday (with slight modifications) regarding a possible small beam > pipe at the STAR IP:> > (1) Physical aperture> We require a 5mm vertical orbit offset and at least 7 transverse rms > beam sizes as> physical aperture. This gives an aperture of 16mm (at injection with Au > beam of> 15mm.mrad emittance, the most limiting scenario).> > Thus a beam pipe radius of 15mm over a length of about 0.5m appears just > possible.> However, this beam pipe *_will become the limiting physical aperture > vertically_*.> And losses that we now typically encounter at the injection or abort > kicker, or in IR4> where a beam pipe with 19mm vertical aperture is installed, may end up > at IP6.> These losses typically happen during the injection setup, or transition > crossing. You must> be able to withstand this. Note that our loss monitors near the > injection and abort kickers> are desensitized during injection and transition crossing, something > STAR may wish to> avoid in the future. (Currently the STAR loss monitor input into the > beam permit system> is masked out according to Mei.)> > To ensure that IP6 it is not the limiting physical aperture, the radius > needs to be increased to> 20mm (given the same amount of orbit errors in all the limiting > locations). It would> then be in the shadow of the IR4 element near the IP with 19mm vertical > aperture.> > (2) Vacuum requirements> We would like to have a NEG coated beam pipe that can be activated (i.e. > it needs> to be bakable to 250C). The allowable dynamic pressure must be specified > by the> experiments (based on allowable beam-gas background considerations). The > vacuum> design must be approved by Dick Hseuh.> > (3) Impedance> To avoid any impedance problems transitions should be smooth.> This is the case in the attached electronic drawing.> > Let me know if I can help you any further,> > Wolfram> > > > Howard Wieman wrote:> > Hi Wolfram,> > > > Here is the model of the beam pipe: > http://www-rnc.lbl.gov/~wieman/TopBeamPipe4.exe > <http://www-rnc.lbl.gov/~wieman/TopBeamPipe4.exe>> > > > You can down load this and run it in windows. There is a measure tool > to get dimensions. As you will see the lengths are a little different > than what I communicated to you from memory. The diameter of the bigger > diameter pipe is 57 mm, smaller than I told you.> > > > Thanks,> > Howard> > > > > -- > > Wolfram Fischer> > Brookhaven National Laboratory> > Bldg. 911B, Upton, NY 11973, USA> > Tel. +1-631-344-5452> -- Wolfram FischerBrookhaven National LaboratoryBldg. 911B, Upton, NY 11973, USATel. +1-631-344-5452
RE: STAR HFT beam pipe