diff --git a/atmat/atphysics/LongitudinalDynamics/BunchLength.m b/atmat/atphysics/LongitudinalDynamics/BunchLength.m
index dabdeee5a..fa9246bff 100755
--- a/atmat/atphysics/LongitudinalDynamics/BunchLength.m
+++ b/atmat/atphysics/LongitudinalDynamics/BunchLength.m
@@ -15,7 +15,7 @@
 % sigmadelta is the energy spread
 % circ is the ring circumference
 % 
-%   see also: atBunchLength
+%   see also: atBunchLength, blgrowth
 
 blg = abs(blgrowth(Ib,Zn,Vrf,U0,E0,h,alpha,sigdelta));
 phi=pi - asin(U0./Vrf);
@@ -24,26 +24,4 @@
 BL = zcBL .* blg;
 end
 
-function blg = blgrowth(Ib,Zn,Vrf,U0,E0,h,alpha,sigdelta)
-% bunch lengthening factor due to the potential well effect
-
-% Ib is the bunch current [A] (it may be a vector for multiple values)
-% Zn is the longitudinal broadband impedance [Ohms]
-% Vrf is the RF voltage [V] (it may be a vector for multiple values)
-% U0 is the energy loss around the ring [eV]
-% h is the harmonic number
-% alpha is the momentum compaction factor
-% sigmadelta is the energy spread
-
-phi=pi - asin(U0./Vrf);
-nus= sqrt(-(Vrf/E0).*(h * alpha)/(2*pi) .* cos(phi));
-
-Delta = -(2*pi*Ib*Zn)./(Vrf*h.*cos(phi).*(alpha*sigdelta./nus).^3);
-Q=Delta/(4*sqrt(pi));
-
-
-
-blg = (2/3)^(1/3)./(9*Q + sqrt(3)*sqrt(-4+27*Q.^2)).^(1/3)...
-    + (9*Q + sqrt(3)*sqrt(-4+27*Q.^2)).^(1/3)./(2^(1/3)*3^(2/3));
-end
 
diff --git a/atmat/atphysics/LongitudinalDynamics/atBunchLength.m b/atmat/atphysics/LongitudinalDynamics/atBunchLength.m
index 5a4f79cc0..d94e6fd70 100755
--- a/atmat/atphysics/LongitudinalDynamics/atBunchLength.m
+++ b/atmat/atphysics/LongitudinalDynamics/atBunchLength.m
@@ -6,17 +6,29 @@
 %
 % Ib is the bunch current [A] (it may be a vector for multiple values)
 % Zn is the longitudinal broadband impedance [Ohms]
-% ring is the at ring without radiation
+% ring is the at lattice (4D or 6D)
+%
 % BL is the bunch length in metres 
 %
-%   see also: BunchLength
+%   see also: BunchLength, blgrowth
 
-rp=ringpara(ring);
-[E0,~,Vrf,h,U0]=atenergy(ring);
-alpha=rp.alphac;
-sigdelta=rp.sigma_E;
+is6d=check_6d(ring);
 circ=findspos(ring,length(ring)+1);
 
-BL = BunchLength(Ib,Zn,Vrf,U0,E0,h,alpha,sigdelta,circ);
-
+if ~is6d
+    [E0,~,Vrf,h,U0]=atenergy(ring);
+    rp=ringpara(ring);
+    alpha=rp.alphac;
+    sigdelta=rp.sigma_E;
+    BL = BunchLength(Ib,Zn,Vrf,U0,E0,h,alpha,sigdelta,circ);
+else
+    [~,ringdata]=atx(ring,1);
+    [~,~,Vrf,h]=atenergy(ring);
+    alpha = ringdata.alpha;
+    E0 = ringdata.energy;
+    U0 = ringdata.eloss;
+    sigdelta = ringdata.espread;
+    bl0 = ringdata.blength;
+    BL = bl0 * blgrowth(Ib,Zn,Vrf,U0,E0,h,alpha,sigdelta);
+end
 end
diff --git a/atmat/atphysics/LongitudinalDynamics/blgrowth.m b/atmat/atphysics/LongitudinalDynamics/blgrowth.m
new file mode 100644
index 000000000..e9ee38c47
--- /dev/null
+++ b/atmat/atphysics/LongitudinalDynamics/blgrowth.m
@@ -0,0 +1,27 @@
+function blg = blgrowth(Ib,Zn,Vrf,U0,E0,h,alpha,sigdelta)
+%  blg = blgrowth(Ib,Zn,Vrf,U0,E0,h,alpha,sigdelta)
+%
+% bunch lengthening factor due to the potential well effect
+%
+% Ib is the bunch current [A] (it may be a vector for multiple values)
+% Zn is the longitudinal broadband impedance [Ohms]
+% Vrf is the RF voltage [V] (it may be a vector for multiple values)
+% U0 is the energy loss around the ring [eV]
+% h is the harmonic number
+% alpha is the momentum compaction factor
+% sigmadelta is the energy spread
+%
+%   see also: atBunchLength, BunchLength
+%
+
+phi=pi - asin(U0./Vrf);
+nus= sqrt(-(Vrf/E0).*(h * alpha)/(2*pi) .* cos(phi));
+
+Delta = -(2*pi*Ib*Zn)./(Vrf*h.*cos(phi).*(alpha*sigdelta./nus).^3);
+Q=Delta/(4*sqrt(pi));
+
+
+
+blg = (2/3)^(1/3)./(9*Q + sqrt(3)*sqrt(-4+27*Q.^2)).^(1/3)...
+    + (9*Q + sqrt(3)*sqrt(-4+27*Q.^2)).^(1/3)./(2^(1/3)*3^(2/3));
+end