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RB26 beam pipe: remove the duplicated RB26/2 plies and restore the missing RB26/3 bellow #61

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sawenzel wants to merge 3 commits into from
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RB26 beam pipe: remove the duplicated RB26/2 plies and restore the missing RB26/3 bellow #61

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249386d
Fix the RB26/2 bellow being filled twice in the beam pipe
sawenzel Aug 23, 2026
c4e16c7
Fix the RB26/2 bellow being filled twice in the Run 4 beam pipe
sawenzel Aug 31, 2026
11c8138
Give the RB26/3 compensator its bellow plies back
sawenzel Aug 31, 2026
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26 changes: 18 additions & 8 deletions Detectors/Passive/src/Pipe.cxx
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Original file line number Diff line number Diff line change
Expand Up @@ -2300,14 +2300,24 @@ void Pipe::ConstructGeometry()
TGeoVolume* voRB26s3Bellow =
new TGeoVolume("RB26s3Bellow", new TGeoTube(kRB26s3BellowRi, kRB26s3BellowRo, zBellowTot), kMedVacHC);

// Positioning of the volumes
z0 = -kRB26s2BellowUndL / 2. + kRB26s2ConnectionPlieR;
voRB26s2Bellow->AddNode(voRB26s2WiggleL, 1, new TGeoTranslation(0., 0., z0));
z0 += kRB26s2ConnectionPlieR;
zsh = 4. * kRB26s2PlieR - 2. * kRB26s2PlieThickness;
for (Int_t iw = 0; iw < kRB26s2NumberOfPlies; iw++) {
Float_t zpos = z0 + iw * zsh;
voRB26s2Bellow->AddNode(voRB26s2Wiggle, iw + 1, new TGeoTranslation(0., 0., zpos - kRB26s2PlieThickness));
// Positioning of the volumes.
//
// A thirteen-convolution bellow has fourteen inner roots, so one lower plie
// leads the thirteen wiggles. The pitch is not 4*PlieR - 2*PlieThickness: a
// torus-and-disc wiggle is longer than the convolution it stands for, and at
// that pitch the stack does not fit the bellow. There is no room to grow it
// either, since only 0.01 cm separates this bellow from the right welding
// tube. The pitch is therefore the one that makes the fourteen roots span the
// bellow exactly, which is 1.5 per cent shorter.
const Float_t kRB26s3PliePitch =
(2. * zBellowTot - 2. * kRB26s3PlieR) / kRB26s3NumberOfPlies;
const Float_t kRB26s3RootToWiggle = 3. * kRB26s3PlieR - 5. * kRB26s3PlieThickness / 2.;

z0 = -zBellowTot + kRB26s3PlieR;
voRB26s3Bellow->AddNode(voRB26s3WiggleL, 1, new TGeoTranslation(0., 0., z0));
for (Int_t iw = 0; iw < kRB26s3NumberOfPlies; iw++) {
Float_t zpos = z0 + (iw + 1) * kRB26s3PliePitch - kRB26s3RootToWiggle;
voRB26s3Bellow->AddNode(voRB26s3Wiggle, iw + 1, new TGeoTranslation(0., 0., zpos));
}

voRB26s3Compensator->AddNode(voRB26s3Bellow, 1,
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26 changes: 18 additions & 8 deletions Detectors/Passive/src/PipeRun4.cxx
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Original file line number Diff line number Diff line change
Expand Up @@ -2165,14 +2165,24 @@ void PipeRun4::ConstructGeometry()
float zBellowTot = kRB26s3NumberOfPlies * (static_cast<TGeoBBox*>(voRB26s3Wiggle->GetShape()))->GetDZ();
TGeoVolume* voRB26s3Bellow = new TGeoVolume("RB26s3Bellow", new TGeoTube(kRB26s3BellowRi, kRB26s3BellowRo, zBellowTot), kMedVacHC);

// Positioning of the volumes
z0 = -kRB26s2BellowUndL / 2. + kRB26s2ConnectionPlieR;
voRB26s2Bellow->AddNode(voRB26s2WiggleL, 1, new TGeoTranslation(0., 0., z0));
z0 += kRB26s2ConnectionPlieR;
zsh = 4. * kRB26s2PlieR - 2. * kRB26s2PlieThickness;
for (int iw = 0; iw < kRB26s2NumberOfPlies; iw++) {
float zpos = z0 + iw * zsh;
voRB26s2Bellow->AddNode(voRB26s2Wiggle, iw + 1, new TGeoTranslation(0., 0., zpos - kRB26s2PlieThickness));
// Positioning of the volumes.
//
// A thirteen-convolution bellow has fourteen inner roots, so one lower plie
// leads the thirteen wiggles. The pitch is not 4*PlieR - 2*PlieThickness: a
// torus-and-disc wiggle is longer than the convolution it stands for, and at
// that pitch the stack does not fit the bellow. There is no room to grow it
// either, since only 0.01 cm separates this bellow from the right welding
// tube. The pitch is therefore the one that makes the fourteen roots span the
// bellow exactly, which is 1.5 per cent shorter.
const float kRB26s3PliePitch =
(2. * zBellowTot - 2. * kRB26s3PlieR) / kRB26s3NumberOfPlies;
const float kRB26s3RootToWiggle = 3. * kRB26s3PlieR - 5. * kRB26s3PlieThickness / 2.;

z0 = -zBellowTot + kRB26s3PlieR;
voRB26s3Bellow->AddNode(voRB26s3WiggleL, 1, new TGeoTranslation(0., 0., z0));
for (int iw = 0; iw < kRB26s3NumberOfPlies; iw++) {
float zpos = z0 + (iw + 1) * kRB26s3PliePitch - kRB26s3RootToWiggle;
voRB26s3Bellow->AddNode(voRB26s3Wiggle, iw + 1, new TGeoTranslation(0., 0., zpos));
}

voRB26s3Compensator->AddNode(voRB26s3Bellow, 1, new TGeoTranslation(0., 0., kRB26s3WeldingTubeLeftL + zBellowTot));
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